Daniel Kahneman (2011, Nobel laureate, the nephew of Rabbi Yosef Shlomo Kahneman, the founder of Ponevezh Yeshiva in Bnei Brak, and in high school and in university was a student of Yeshayahu Leibowitz) presents a fascinating description of how the human mind works, that there are two systems in the brain. The first system immediately appraises situations and responds intuitively, while the second system responds slower and with more thought. The second system is the "conscious reasoning self" but its usage involves more effort and work. The second system has the ability to override the first system, but it is lazy. Thus, the natural inclination is for the first system to function, but when it is stymied, then the second system takes over.
This distinction in the thinking process of the human mind can explain the different terminology, va-yachbed and ve-yechezak. The word va-yachbed refers to the first system of thinking that intuitively Pharaoh would refuse to let the people leave Egypt, while the word ve-yechezak refers to the second system of human thought that after some thought Pharaoh would refuse to let the Jewish people leave Egypt.
4:21 records that notwithstanding all of the wonders that G-d would do, G-d would achazek the heart of Pharaoh until the tenth plague. The wonders could refer to the three signs recorded in 4:3,6,9 or maybe the first nine plagues, but in any event, after a repeated set of miracles, both the intuitive reaction and thoughtful re-action would be for a person to be impressed and let the Jewish people go. However, in 4:21, G-d says that by these cases, G-d would harden Pharaoh’s heart that G-d would cause Pharaoh to concoct reasons why these set of signs were not significant, and this thinking is indicative of the second system of thinking. Thus, even if Pharaoh was impressed intuitively and would be inclined to let the people go, G-d made sure that his system two caused him to refuse to let the Jewish people leave Egypt.
The next reference to G-d hardening Pharaoh’s heart is 7:3, but here the word used is aksheh, which covers both ways of thinking.
The next case of Pharaoh’s heart being hardened is 7:13, which uses the word ve-yechezak after Aharon's staff swallowed the staff of the Egyptian magicians. (This miracle might refer back to 4:21.) This miracle was impressive, and the intuitive response would have been to agree to let the people leave. However, Pharaoh's system two of thinking took over, and he might have reasoned that this was only one trick or he was unimpressed for another reason, so he did not agree to let the Jewish people go.
In the following verse, 7:14, before the first plague, G-d told Moshe that Pharaoh's heart was hardened. The word used is cabed, which means that G-d was telling Moshe that Pharaoh's intuitive thoughts, gut impulse, was not to free the Jewish people, as the miracle of the swallowing of the staffs was then “ancient history” for Pharaoh.
By the first plague, Moshe turned the Nile into blood in front of Pharaoh, see our discussion on 7:14-25, “A bloody mess.” This act surely impressed him and should have changed his gut impulse to let the Jewish people leave. However, afterwards, his magicians were also able to turn water into blood. Even though the magicians' act was not as impressive as turning the Nile into blood, still this was enough for Pharaoh's second system to override his impression from Moshe's act, and then the Torah uses the word ve-yechezak, 7:22.
At the end of the next plague, frogs, 8:11 records that ve-hachbed the heart of Pharaoh. Here Pharaoh’s intuitive re-action at this point was not to be swayed by the plague since the plague was over, and there was no need for him to rationalize why the miracle was not impressive.
By the third plague, the magicians admitted that the plague was an act of G-d, 8:15, so Pharaoh's intuitive response should have been to agree to let the Jewish people go. However, again his second system overcame his intuition, he refused to let the people go, and the Torah uses the word ve-yechezak. (A possible reason for why Pharaoh did not listen to his magicians, is because they knew all along that they were not able to duplicate the plagues and that G-d was helping them, but Pharaoh thought that they really had the ability to duplicate the plagues. Thus, by the third plague, the magicians admitted what they already knew, but for Pharaoh, this was the first time that the magicians could not copy the plague, and for him one time was not enough to lose his slaves. I thank Eric Sommers for this idea.)
At the end of the fourth plague, 8:28 records that va-yachbed Pharaoh of his heart since, just like by the end of the second plague, once the plague was over, then his intuitive re-action was to be unimpressed.
Similarly, by the end of the fifth plague, 9:7 records that va-yechbad the heart of Pharaoh. Again, once the plague was over, then there was no need for a great justification for why the plague should not persuade him to let the Jewish people leave. Instead, Pharaoh followed his first system of intuitive thinking to not let the Jewish people leave Egypt.
The sixth plague, boils, was a very painful plague, and again as by the third plague, his magicians were unable to stop the plague. Accordingly, Pharaoh's intuitive response and his second system of thinking should have been to let the Jewish people leave. However, by this plague, the Torah specifically records that G-d intervened, 9:12. The idea here is that G-d intervened by Pharaoh’s second thoughtful system to not let the people go, possibly by not having the plague affect Pharaoh, and the Torah uses the word ve-yechazek, 9:12.
The seventh plague, hail, is where the Torah uses both ve-yachbed and ve-yechezak. First, 9:34 records that Pharaoh saw that the plague ended, and hence his intuitive response, as by the end of the second, fourth and fifth plagues, was not to let the people go. Thus, the Torah uses the word ve-yachbed. However, after seven plagues, Pharaoh should have thought some more, and his second thoughtful system should have overcome his intuitive reaction, and agreed to let the people go. Yet, in 9:35, the Torah uses the word ve-yechezak to indicate that for some reason (G-d intervened?) Pharaoh’s second system of thinking convinced him not to agree to let the Jewish people go.
The following verse, 10:1 then records that G-d hecbadeti the hearts of Pharaoh and his advisors. This verse apparently refers to all of the plagues up to this point, and the idea would be that G-d made it that both Pharaoh and his advisors’ intuitive thoughts (their first system of thinking) were not to let the Jewish people go since at that moment there was no plague or a threat of a plague. Yet, there was a difference between Pharaoh and his advisors. After hearing the warning about the next plague, the eighth plague, locusts, Pharaoh's advisors urged him to let the Jewish people leave, 10:7. By these advisors, their second system of thinking was overcoming their first system of thinking and G-d did not harden their second system of thinking to stop it from overcoming their first system of thinking. However, by Pharaoh, G-d also hardened his second system of thinking, as indicated in 9:35, and Pharaoh refused to let the people go, 8:11.
In the following two plagues, locusts and three days of darkness, the Torah only uses the word ve-yechezak, 10:20,27. In these cases, even after the plague was over, due to the cumulative number of plagues, Pharaoh’s second thoughtful system of thinking should have overcome his intuitive system of thinking and he should have agreed that the Jewish people could leave. However, since there was a desire for there to be the tenth plague, G-d hardened Pharaoh's second system of thinking that he would not let the Jewish people leave Egypt. Similarly, 11:10 records that G-d va-yichazek the heart of Pharaoh since after the nine plagues, Pharaoh’s second system of thinking should have led him to let the Jewish people go, but G-d intervened that Pharaoh’s second system of thinking convinced Pharaoh not to let the Jewish people leave Egypt.
The final cases where G-d hardened Pharaoh’s heart was by Yam Suf, 14:4,8,17, and here the words are ve-chizakati, va-yechzak and me-chazek. After the ten plagues, the second thoughtful system of thinking should have convinced Pharaoh and the Egyptians not to chase after the Jewish people at Yam Suf, but G-d wanted there to be the miracle of Yam Suf, see our discussion on 14:4-31, “The miracle at Yam Suf: Bait.” Accordingly, G-d hardened Pharaoh's and his soldiers second system of thinking to chase after the Jewish people and hence the word used is va-yechzak or its variations.
Bibliography:
Kahneman, Daniel (1934-2024), 2011, Thinking, fast and slow, New York: Farrar, Straus and Giroux
Kahneman, Daniel (1934-2024), 2011, Thinking, fast and slow, New York: Farrar, Straus and Giroux