Vayikra 25:8-11 (Behar) - From yovel to yovel: 49 or 50 years?

Vayikra 25:8,9 record that the people are to count 49 years, and then on Yom Kippur the shofar is to be blown. 25:10 then records that the 50th year is kadosh, the slaves are to go free, the year is called yovel, and each person can return to his ancestral home. The Torah does not explain how the count is to begin after the yovel year, and this had led to various opinions.

The Talmud records an argument as to when the new cycle begins. One opinion, the Rabbanim (Nedarim 61a, Rosh Hashanah 9a), explains that the yovel year stands alone, that it is not part of the 49 year cycle (shemitta years 7,14,21,28,35,42,49, yovel year 50). This means that year 51 begins a new cycle, shemitta years 57,64,71,78,85,92, 99, and the next yovel is year 100 . Year 101 begins a new cycle and year 150 is the third yovel year. With this system there are two consecutive years of not working the land, years 49 and 50, or years 99 and 100, etc., and the yovel year breaks up the seven year cycles of shemitta. This system is accepted by the Rambam (Laws of shemitta and yovel, 10:7) and Kawashima (2003).

The second opinion in the Talmud is Rabbi Judah ben Ilai (again Nedarim 61a and Rosh Hashanah 9a and Bergsma 2005) that the yovel year is part of the 49 year cycle. The idea is that the 50th year counts both as part of the previous cycle (shemitta years 7,14,21,28,35,42,49, yovel year 50) and is also part the first year of the next cycle (shemitta years 56,63,70,77,84,91,98, yovel year 99). With this cycle, year 99 is the second yovel year and begins the third cycle. The third yovel is year 148. This approach is similar to the first approach that there are two consecutive years of not working on the land (shemitta and yovel), but it differs from the first opinion since there are only 49 years from one yovel to the next and also there is no break in the counting of seven years of shemitta. However, as pointed out by the Talmud (Nedarim 61a), this approach is problematic since during the seven year cycle which includes a yovel year, the people can only work five years, while the Torah states that the people will work six years, and then rest in the seventh year, 25:3,4.

The Talmud in Nedarim notes that both opinions cannot explain verses 25:20-22, which record that the crops in the sixth year would be sufficient until the crops that are planted in the eighth year are reaped in the ninth year. The Torah is referring to the land lying completely fallow for only one year, but according to both opinions, there is a possibility that the land lies fallow for two years, when a yovel year follows a shemitta year, which would mean that the crops from the sixth year would have to last four years until the tenth year. 

A third approach, which is possibly the opinion of R. Judah (in Talmud Rosh Hashanah 9a but not in Nedarim 61a), follows the second opinion that the yovel year is every 49 years, but maintains that the yovel year was also a shemitta year. The difference between the two approaches is that according to the second opinion the first year in the first cycle is a regular year, while according to the third opinion the first year in the first cycle was a special or shemitta year. According to third approach, the phrase in 25:2, "the land will rest, a Shabbat to G-d," is not a general statement, but indicating that the beginning of the count was a year of rest, though not necessarily a regular shemitta year. The next shemitta year would be year eight in the cycle and then the seventh shemitta year would be year fifty of the cycle, the yovel year, (shemitta years 8,15,22,29,36,43,50, yovel year 50) and the first year with regard to the count of the next fifty years (shemitta years 57,64,71,78,85,92,99, yovel year 99). Year 99 is 49 years from the previous yovel in year 50, and also the fiftieth year counting year 50 as the first year. The third cycle would be shemitta years 106,113,120,127,134,141,148 and yovel year 148. Again, year 148 is 49 years from the previous yovel year in year 99, and the fiftieth year counting year 99 as the first year in the cycle.

This approach accords with 25:20-22 since there are never two years when the land is not worked, and with 25:3,4 since there are always six years of work between each shemitta. In addition, this approach matches the counting by sefirat ha-omer in 23:15,16, that the first day that begins the count is a holiday, the offering of the omer sacrifice, and the fiftieth day, is also a holiday, Shavuot, and so too here the first and last years are shemitta and yovel years.

According to the third approach, why does the Torah (25:11) list the agricultural restrictions of the yovel year if in any event the year was a shemitta year? The answer is that had the restrictions not been motioned, then a person might have thought that the yovel year superseded the shemitta year, and there would be no restrictions in that particular shemitta year.

The most recent proponent that I saw of the third approach is Hye Kim (2010) and he makes the interesting point that this double counting (counting the same year, year 50, 99, 148, etc., as both the last year of one cycle and the first year of next cycle) accords with the counting in Shemot 19:10-11, Vayikra 7:16-19, and Vayikra 19:6,7.

In conclusion, the third approach best accords with the text.

Bibliography:

Hye Kim, Young, 2010, The Jubilee: Its reckoning and inception day, Vetus Testamentum, 60, pp. 147-151.

Kawashima, Robert, 2003, The Jubilee, every 49 or 50 years? Vetus Testamentum, 53:1, pp. 117-120.

2015 version of my commentary on the Haggadah is now available

Hello,

The 2015 version of my commentary on the Haggadah (54 pages) is now available. It has some additions/ corrections/ revisions from the previous versions.  If you are interested in receiving the commentary, please send me an email, ajayschein@gmail.com, and I will send you the file.  I wish everybody a chag kasher ve-samaech.

Andrew Schein  

Vayikra 10:16-20 – The argument between Moshe and Aharon after the deaths of Aharon's sons: An argument for the sake of heaven

Vayikra 10:16-18 records that Moshe learned that the hatta’t sacrifice from the ceremony of the eighth day had been burnt, and this made him angry since he thought the sacrifice should have been eaten. Aharon defended the burning of the hatta’t by saying, 10:19, “Here, today, they brought their hatta’t and olah offerings, before G-d, and such things as these happened to me! Had I eaten the hatta’t today, would it have pleased G-d?” (Variation of Fox, 1995, translation.) 10:20 records that Moshe accepted Aharon’s response.

Why did Moshe believe that the sacrifice should have been eaten, and why did Aharon disagree? In 10:19, Aharon was referring to the deaths of his sons, but why should their deaths have caused him not to eat the hatta’t? Finally, why did Moshe accept Aharon’s response? (My understanding of this section began with a conversation with David Linzer in March 1992, though since then, notably in March 2014, I have changed some of my views of this section.)

In order to understand this argument, we need to clarify which hatta't is being argued about. 10:16 describes the hatta’t as being a goat, and 9:3 records that as part of the sacrifices of the eighth day the people were to bring a hatta’t that was a goat. This would seem to be the only possible reference to the hatta’t in 10:16, see Luzzatto on 10:16. R. David Hoffmann (on 10:16) notes that R. Akiva follows this understanding. However, Rashi (on 10:16) quotes the majority view of Chazal that the sacrifice was the hatta’t that was brought on the new moon (Bemidbar 28:5), which was an additional sacrifice to the sacrifices for the ceremony of the eighth day. Rashi (on 10:17) notes that Moshe said that the eating of the hatta’t was to bring atonement for the people (10:17) and the approach of Chazal is that the hatta’t of the new moon was to bring atonement for causing tumah in the Mikdash. Luzzatto rejects this "proof" since 9:7 records that the hatta’t of the people was to bring atonement for the people.

Rashi's explanation is based on the understanding that eighth day of the initiation of the priests was also the first day of the first month of the second year of the people’s stay in the desert. I doubt that the ceremony of the eighth day was on the first day of the first month in the second year of the people's stay in the desert since I believe that the seven day initiation process of the priests began on either the 15th or the 22nd of the first month of the second year, see our discussion on Shemot 40:1-33, "The anointing of the mishkan, the ohel moed and the priests."

The next point to clarify is what type of hatta't was the hatta't of the people. There are two types, the inner hatta't and the outer hatta't. By the inner hatta’t, the blood of the animal is sprinkled on the parokhet within the mishkan proper, and the parts of the animal that are not offered on the altar are burnt, 4:1-21, 7:23. By the outer hatta’t, the blood is only sprinkled on the altar outside the mishkan proper and the parts of the animal that are not offered on the altar are eaten by the priests, 4:22-35, 7:17-22. The hatta't of the people was an outer hatta't since the blood was sprinkled on the outer altar, 9:9,15. Accordingly, Moshe stated that the hatta't was to be eaten since the blood of the sacrifice had not been brought into the mishkan proper where the inner altar was located, 10:18.

Moshe was worried that there was a danger that because the sacrifice had not been eaten, all the people would be punished. 10:6 records that Moshe told Eleazar and Itamar, Aharon’s two surviving sons, that they should not engage in any mourning rites since they could die and there could be a ketsef on the people. The term ketsef indicates that G-d is angry and that there can be an ensuing punishment, see Bemidbar 17:11. Thus, just like Moshe was concerned that mourning rites could cause G-d to punish the people, so too he was worried that the non-eating of the sacrifice could also cause G-d to punish the people. We now understand Moshe's argument, but why did Aharon disagree if it was so important for the sacrifices to be eaten?

Rashi (on 10:16) quotes two opinions of Chazal to explain Aharon’s response. One, Aharon maintained that since he and his sons were mourners for Nadav and Avihu, they were not allowed to eat the sacrifice. The idea being that the law of mourning would override the usual law that the outer hatta’t was to be eaten. Luzzatto (on 10:17) rejects this approach since Moshe had already told Aharon and his sons that they were not to act as mourners (10:6,7), which means that in all cases they were not to follow the laws of mourning. Luzzatto (on 10:19) also adds that Aharon began his argument by referring to the hatta’t and the olah, 10:19, but this reference is irrelevant if the rationale was that they were mourners. In addition, how did Aharon know that the laws of mourning precluded eating from the sacrifices, something clearly unknown to Moshe?

Rashi's (on 10:16) second approach for understanding Aharon’s argument is that there was some tumah attached to the hatta’t and thus Aharon did not want to eat the sacrifice. Milgrom (1991, pp. 635-640) develops this approach. He argues that the deaths of Nadav and Avihu transformed the hatta’t of the people from an outer hatta’t to an inner hatta’t since their deaths raised the level of tumah of the hatta’t that the sacrifice had to be burnt. This understanding accords with his view that in general a hatta’t is to remove tumah, and the reason why an inner hatta’t is burnt is because the level of tumah the sacrifice is removing is so large that the hatta’t cannot be eaten.

I doubt that Aharon did not eat the hatta't since it was tamei because there is no connection between this explanation and Aharon's response to Moshe. According to Milgrom's explanation, why did Aharon refer to his sacrifices that he had offered beforehand? According to Milgrom, Aharon was not permitted to eat the hatta’t, so why did Aharon not simply say something like "I cannot eat it since it is tamei."

Also, how did the sacrifice become tamei? Milgrom writes that “that the deaths of Nadav and Avihu in the midst of sacred precincts polluted the entire sanctuary.” Yet, according to the laws of tumah (Bemidbar 19) death only causes tumah, when the body is in a tent with a roof, but this did not occur here as Nadav and Avihu died outside of the mishkan proper, 10:4, and see our discussion on Vayikra 10:1,2 "Nadav and Avihu,"  In addition, the hatta’t sacrifice should not have become tamei because the supposed cause of the tumah (Nadav and Avihu's sin) occurred after the sacrifice was offered and its blood was sprinkled, and there is no indication that Nadav and Avihu died when touching the hatta’t. 
Finally, why did Moshe not know that the deaths of Nadav and Avihu generated so much tumah that the hatta’t could not be eaten? It seems to me that Milgrom is forcing his theory of hatta’t and tumah into this episode.

These two approaches are legal arguments as to why Aharon and his sons burnt the hatta't, and instead two psychological arguments have been suggested.

Rashbam (on 10:19) suggests that Aharon was claiming that after the deaths of his sons, he and his remaining sons were too sad to eat the sacrifice. N. Leibowitz (1980, p. 74) likes this approach. She explains that sacrifices must be offered in the proper state of mind, and Aharon could not fulfill this requirement in his state of grief. This approach is similar to the mourning approach but it stresses personal feelings as opposed to a point of law. Yet, where does this idea come from that one cannot be in a state of grief when one eats sacrifices? If there was a need to eat the sacrifices to help the people, then why were the personal feelings of Aharon and his sons relevant? How did Aharon know that G-d would not accept his eating if he was sad? Also, Luzzatto points out that this explanation does not explain why Aharon referred to his personal sacrifices, his hatta’t and his olah? According to this idea, Aharon should have just said "After the events of the day, I am too sad to eat the hatta't."

Luzzatto suggests that the argument between Moshe and Aharon was whether the eating of the hatta’t could lead to atonement for the people. Moshe wanted the hatta’t to be eaten in order for the people to attain atonement, 10:17. Aharon responded that he and his sons had already offered sacrifices that day, and still his sons died. Thus, he understood that his sacrifices did not lead to atonement for himself. Aharon continued and said, “Had I eaten the hatta’t today, would it have pleased G-d?” Aharon doubted that his eating of the hatta’t of the people could lead to atonement for the people once he was not able to bring atonement for himself from his own sacrifices.

This explanation accords with all of Aharon’s statement in 10:19 and makes Aharon’s statement a rebuttal to Moshe’s argument in 10:16-18. Yet, how did the deaths of Nadav and Avihu show that Aharon did not attain atonement from his sacrifices since it seems that they died for their own sins? Luzzatto writes that Aharon felt that he was out of favor with G-d, but from the death of his sons he should only have known that his sons had fallen out of favor with G-d not himself. Perhaps he was a father feeling guilty about his children’s deaths, as maybe he felt that it was his actions by the sin of the golden calf which caused his sons to die, see Rashi on Devarim 9:20. Moshe did not have this feeling so he initially wanted Aharon to eat the sacrifices following the law of the outer hatta’t. However, after Moshe heard Aharon’s claim, he accepted the idea that Aharon felt that he had not attained atonement from his sacrifices and hence he could not help the people attain atonement.

N. Leibowitz (p. 73) likes Luzzatto’s approach in that it accords with the idea that Aharon was giving expression to his personal feelings, but she rejects the explanation since she claims that “a sense of guilt does not free a man from responsibility to perform his duties.” This is similar to the question on the Rashbam's approach, that if it was Aharon and his son's responsibility to eat the hatta't and they were not allowed to mourn, then they had to eat it, whether they felt guilty or sad.

Maybe the argument between Aharon and Moshe is a basic argument about the value of sacrifices, akin to the argument many years later between the Rambam and the Ramban, see our discussion on Vayikra 1:9, "How can one understand sacrifices in the Torah?" Aharon was pointing out that the events of the day showed that sacrifices were ineffective. Aharon noted that he and his sons had just offered a hatta't and an olah, and yet his sons were killed almost immediately afterwards. What point was there for him to eat the hatta't? Aharon was rebutting Moshe's claim that the non-eating of the hatta't would lead to a ketsef not due to sadness or guilt but because he doubted that his eating of the sacrifices would please G-d to stop a ketsef if G-d decided to send ketsef. This would be analogous to the Rambam's view of sacrifice in the Moreh, 3:32, that sacrifices were only commanded since the people could not envisage a religion with sacrifices.

With this idea, Moshe had initially thought that sacrifices had to be eaten since either he thought that sacrifices were effective to bring atonement (like the Ramban) or because one had to do what was commanded, but he agreed to Aharon's point. This could be because he accepted that sacrifices are not effective in general or that in this case they were ineffective. 

A reason why in this particular case they were meaningless is that if the point of offering sacrifices is because one is demonstrating one's devotion to G-d, then here where Nadav and Avihu acted not according to G-d's will (10:1), then any sacrifice that they did would also become meaningless. Note that according to this idea, once Moshe accepted Aharon's opinion, then Aharon and his sons would not have eaten the minhah and the shelamim, 10:12-15.

If this is understanding is correct, then this episode supports the Rambam's opinion that really G-d does not want our sacrifices. If this is the message of this episode, then this would have been the most appropriate place to make this point, right after the laws of the sacrifices and the initiation of the priests. Furthermore, it is telling that it is the high priest, Aharon, who rejects sacrifices.

Bibliography:

Fox, Everett, 1995, The Five Books of Moses: A new translation, New York: Schocken Books.

Leibowitz, Nehama (1905-1997), 1980, Studies in Vayikra, translated by Aryeh Newman, Jerusalem: The World Zionist Organization.

Milgrom, Jacob, 1991, 2000, 2001, Leviticus: The Anchor Bible, New York: Doubleday

Shemot 25:31-40 – The menorah in the mishkan: A burning tree

Shemot 25:31-40 records the instructions to construct the menorah, the lampstand, as one of the pieces of furniture within the mishkan. Why was the menorah in the mishkan?

One possible answer is due to the lights of the menorah (25:37). Was there a need to have lights in the mishkan? One might answer that it is obvious, people need light to see. However, from Shemot 27:21 and Vayikra 24:3 it seems that the lamps were lit only at night since apparently during the daytime, some sunlight was able to provide light inside the mishkan through the one side where there was only one veil, 26:36,37, as most likely, the veil was not that thick to stop light from passing through. (Note, the Talmud, Shabbat 22b, quotes Rav that the western light on the menorah was used to light the other lights because this light burnt all day, and apparently this was the practice in the Bet ha-Mikdash, see Ramban on 27:20.)

Was anybody in the mishkan at night? The Torah never records anybody entering at night, but maybe when the menorah was lit at twilight (30:8) there was a need for light just then. Another possibility is that the Abravanel (on 27:20,21, 1997, p. 462, also see N. Leibowitz, 1976a, p. 512) writes that Moshe was able to enter the mishkan at all times, and Moshe would have needed the light if he came into the mishkan at night.

Rashbam (on 25:31, quoted also by Bekhor Shor and Hizkuni) writes that the lights from the menorah were to illuminate the table. Yet, the Rashbam does not explain why there was a need to illuminate the table.

Rambam (Moreh 3:45, see also Amos Chacham, 1991, vol. 2, p. 280) writes that the lights were in order to glorify and honor the Bet ha-Mikdash. Apparently he believes that the light would enable people to see the rooms of the Bet ha-Mikdash and this vision would increase their awe of the Bet ha-Mikdash. (I believe though I am not positive that the Rambam was also referring to the mishkan.)

Another possibility is that the lights on the menorah symbolized the revelation of G-d, see Zechariah 4:6 and statement by Rav Sheshet in Shabbat 22b. This symbolism could be the reference to the statement in 27:21 that the lighting of the menorah was before G-d, see Amos Chacham (1991, on 27:21). This idea explains why there was a need for light, but the Torah records that the menorah had an intricate design. Do the details relate to the lighting? Were the details just for decoration?

N. Leibowitz (1976a, p. 500) notes that while the Rambam was unconcerned with the details of the menorah, many commentators believed that there had to be some lesson to be learned from these details. She quotes Abravanel who suggested that all the aspects of menorah relate to knowledge, and the Alshikh who relates them to moral qualities. However, she notes that allegoric explanations, such as these, are subjective. Yet, there is one approach that has been developed at least since the 19th century that accords with the simple reading of the text.

In a lengthy excursus on the menorah, S.R. Hirsch writes (1989, pp. 459,460), "If we picture its whole appearance, with its flowery base, its stem and arms with their almond shaped cups, knobs and flowers, the whole appearance strikes one as a tree,… blossoming upwards from its root,… a golden tree." Similarly, Benno Jacob (1992, p. 906) writes of the menorah that "its description… leaves no doubt that we are dealing with a unified organism which was to possess the form of a stylized tree." Likewise, Sarna (1991, p. 165) writes, "the shape of the lampstand - the trunk with its branches extending on either side - unmistakably evokes the image of a tree."

The idea explains why all the pieces of the menorah were to be made together from one block of gold (25:36), and not joined together after they were fashioned since the menorah was one unit like a tree. The base of the menorah is a yerech (25:31), which would be like the roots of the tree. The word the Torah uses for the main shaft and the sides going up is a kaneh, which is a reed. The seven kanim were decorated with gaviaim, kaftorim and perahim, all of whom relate to flora. The gavia is referred to as being almonds (25:33), the kaftor were apple shaped according to Rashi (on 25:31), and perahim are flowers. They would be like fruit on the branches of a tree.

Why was there an image of a tree in the mishkan? Various suggestions have been offered. Hirsch refers to the tree of knowledge, but I did not understand the connection. Benno Jacob suggests that the menorah parallels Aharon since he was the first in the family tree of priests. Sarna writes that possibly the imagery is to represent the tree of life, but he does not explain this relationship. Everett Fox (1995, p. 402) writes that trees "connote permanence, growth, and majesty- in other words a reflection of the divine."

Maybe trees symbolize a connection between man and G-d. A tree begins in the ground and grows upward towards the heavens. In the Garden of Eden, it was the trees and their fruit which were the bridge between G-d and mankind. When Adam and Chava ate from the fruit of the tree of knowledge, they became G-d like, Bereshit 3:22. If they had eaten from the tree of life, then they would have had eternal life, and again been similar to G-d, see our discussion on Bereshit 2:9,17 "Two trees."

The two ideas of light and the image of a tree can be combined, as together they give the image of a fire on a tree. This might be the imagery by the burning bush, Shemot 3:2. In addition, and this could be the reason for the burning bush, when Moshe went up on Mount Sinai to get the luchot, the people saw the glory of G-d as a burning fire, 24:32. This burning image would have been seen by the person who lit the menorah, and maybe by the people if they were able to see the menorah lit up from outside the mishkan.

In our discussion on chapters 26,27, "The three zones of the mishkan and the covenantal process," we suggested that the mishkan represents different aspects of the covenant. Every covenant has some type of revelation. By the covenant at Mount Sinai, the revelation was the people's vision of the glory of G-d (also 24:10,11). Accordingly, if the menorah was able to evoke that vision, then the menorah was also a symbol of the covenant.

Bibliography:

Abravanel (1437-1508), 1997, Commentary on Shemot, Jerusalem: Horev

Chacham, Amos, 1991, Da'at Mikra: Commentary on Shemot, Jerusalem: Mossad Harav Kook.

Fox, Everett, 1995, The Five Books of Moses: A new translation, New York: Schocken Books.

Hirsch, S. R. (1808-1888), 1989, The Pentateuch, rendered into English by Isaac Levy, second edition, Gateshead: Judaica Press.

Jacob, Benno (1869-1945), 1992, The second book of the Bible: Exodus, translated with an introduction by Walter Jacob, Hoboken: Ktav Publishing House.

Leibowitz, Nehama (1905-1997), 1976a, Studies in Shemot, translated by Aryeh Newman, Jerusalem: The World Zionist Organization.

Sarna, Nahum (1923-2005), 1991, The JPS Torah Commentary: Exodus, Philadelphia: The Jewish Publication Society.

Shemot 8:16-28 - The fourth plague in Egypt: Arov

Shemot 8:16-28 records the plague of arov, the fourth plague, but today nobody knows what exactly it was. The word arov implies a mixture of something, but a mixture of what?

Josephus writes that arov was a mixture of wild animals while Philo suggests that it was types of flies (quoted in Jacob, 1992, pp. 266,267). This argument continued in the Midrash. Shemot Rabbah (11:3) quotes that R. Yehuda suggests that the fourth plague was a mixture of wild beasts, while R. Nehemiah argues that the plague was gnats and hornets. The author of the Midrash favors R. Yehuda since he notes that 8:27 records that G-d removed all of the arov, which suggests that the arov had some value being dead, which he claims is the skins of the wild beasts. Possibly for this reason, this definition has become the traditional approach, see Rashi and Ibn Ezra on 8:17.

Luzzatto (on 8:17) argues that arov cannot be wild beasts since 8:17,20 record that the arov entered the house of the Egyptians, and if it was wild beasts then the people could have closed their doors and kept the animals outside. Furthermore, Benno Jacob (1992, p. 266) argues that arov cannot be wild animals since the plagues were not meant to be lethal, while if there really were wild animals then the plague would have killed large numbers of the Egyptians something not mentioned in the Torah. Yet, if arov is a mixture of insects, then it seems to have been almost identical to the previous plague, kinnim.

One clue to the difference between arov and kinnim is that the kinnim appear to have been in the air like dust and they affected people and animals, 8:13, while the arov was on the ground and seems to have affected the Egyptian homes, 8:17,20. In addition, the Torah does not record any damage due to the kinnim. Kinnim, which was the third plague in the first set of three plagues, appear to have been annoying as were the other two plagues (blood and frogs) in the first set of plagues. On the other hand, 8:20 records that the arov caused great destruction, but what was the destruction? It could not have been the destruction of the crops since that occurred later by the plagues of hail and locusts, 9:31, 10:15. The Torah twice refers to the arov as entering the homes of the Egyptians, 8:17,20, and on the second occasion this description precedes the statement that the arov caused great destruction.

My guess is that kinnim were insects that fly while arov were terrestrial insects. Some terrestrial insects (ants, termites) can cause great destruction to homes, and then the destruction attributed to the arov was to the Egyptian homes, something unique in the plagues. I am not sure what the Egyptian homes were made of, wood, stone, mud, and/ or dung, but the arov could have been a mixture of terrestrial insects that were able to eat through the building materials of the Egyptian homes.

8:18,19 note that the plague of arov would only affect the Egyptians, G-d would make a division (pedut) between the Jewish people and the Egyptians by this plague, and the plague would be a sign of this division. This distinction was not just that by the Jews there were no insects, while by the Egyptians there were insects, as this was the only plague that the Torah specifically states that it would be a sign (ot) of the division or separation between the Jews and the Egyptians.

What was the sign from the plague of arov? When terrestrial insects appear in the multitudes, they cover the ground, which takes on the color of the insects. However, since the insects did not enter the land of Goshen, they would have formed a line on the ground between the land of Goshen and the rest of the Egypt, which would be the sign that the plague only affected the Egyptians and not the Jewish people.

(There were other plagues where this division was very evident, as for example the plagues of darkness and the deaths of the Egyptian firstborn sons, 11:6,7, but the Torah does not use the word ot by these plagues. The word ot does appear by the blood on the homes, 12:13, and I believe that the sign here by arov would be similar to the sign of the blood, which was a red line.  It is possible that the Torah makes a point of the plague of arov being a sign of this division between the Jews and Egyptians since this was the first plague where this division occurred, see Ibn Ezra on 7:24.)

Bibliography:

Jacob, Benno (1869-1945), 1992, The second book of the Bible: Exodus, translated with an introduction by Walter Jacob, Hoboken: Ktav Publishing House.