Bereshit 31:17-21 record that Yaakov left Haran secretly without telling Lavan, and that Rahel stole her father’s terafim. Lavan chased down Yaakov and then searched for the terafim, which he did not find, 31:22-35. After Lavan gave up looking, Yaakov gave an impassioned speech about how hard and honestly he had worked for Lavan, 31:36-42. This incidence raises several questions: What were the terafim? Why did Rahel steal them? And, what is the significance of the terafim?
What were the terafim? There are at least three opinions. One approach is that the terafim were a type of family idols. Another approach is that the terafim were items that were used for divination. Finally, a third approach is that the terafim were ancestor figurines, see Van der Toorn (1990).
Why did Rahel steal the terafim? Rashi (on 31:19) quotes from the Midrash that it was to stop her father from worshipping idols. Ibn Ezra (on 31:19) questions this approach because why then did Rahel take the terafim with her instead of burying them? Was there not enough time to dispose of the terafim?
Ibn Ezra (on 31:19, also see Rashbam on 31:19) writes that Rahel stole the terafim in order that Lavan would not have been able to use the terafim to follow them. This accords with the Ibn Ezra’s belief in astrology, but if true, Rahel’s plan failed completely since Lavan seems to have had no trouble catching up to Yaakov.
Gordon (1937) and Speiser (1964, pp. 250,251) note that a case in Nuzi laws (documents from a town in present day Iraq 14, 15th centuries BCE) shows that family gods could be a sign of property rights within the family. With this idea, Rahel took the terafim to be able to make a claim for these rights. (They also claim that from the Nuzi laws that Yaakov had a status of an adopted son with regard to Lavan, but I doubt this since an adopted son would mean that Yaakov would have had to stay with Lavan, and theoretically Yaakov always intended to leave Lavan.)
Moshe Greenberg (1962) doubts this archeological approach since we never hear that Rahel or Yaakov made such a claim, and we see that Yaakov separated from Lavan apparently forever . However, prior to Rahel taking the terafim, she did state that Lavan had mistreated her and her sister by not giving them their dowry (31:15), so then she could have taken the terafim to later be able to make a claim to get her due rights. However, after Lavan and Yaakov made their treaty, 31:52, then they relinquished any financial claims on each other, which would explain, according to this archeological approach, why Rahel (or Yaakov) could not have used the terafim to later stake any claim on her father’s property.
Greenberg suggests (see also Kass, 2003, pp. 436-439), based on a quote from Josephus (not on this incident), that Rahel was following a common custom that a person would take their household gods with them when travelling, presumably for good luck or to worship. Yet, even if Rahel wanted the terafim to worship them, did she have to take her father’s idols? Were these the only idols in the family? More likely, if she always believed in these idols, then she would have her own idols. Why did she have to take her father’s idols? Was Lavan’s idol the most important idol?
Benno Jacob (1974, p. 210) notes the possibly that Rahel took the terafim to take revenge on her father. With this idea, Rahel’s motive might have been to get back at Lavan for ruining her life by switching her and Lea or for taking her dowry. With the former idea, she had retained her desire for revenge all the years (13) since the wedding.
What is the significance of the terafim? Alfred Hitchcock described a technique that he called McGuffin, which he used in his movies. The technique is that the plot of the movie revolves around some item, which the characters care deeply about, but the item itself has no real importance. The crucial issue is the interaction of the characters, but not the item that the characters claim to care about.
The terafim are a McGuffin. The characters care deeply about the terafim, but the terafim are not important as Rahel could have stolen gold or an animal from her father. The importance of the terafim is that when Lavan searched and could not find the terafim, this caused Yaakov to be indignant, and this indignation led to Yaakov’s passionate speech about his working conditions with Lavan, 31:36-42. Previously, in his dealings with Lavan, Yaakov meekly accepted whatever Lavan said as by his marriage and working conditions, 29:15,26-28,27. However, this search, which was so degrading, caused a "breaking point" in Yaakov, that now finally he spoke his mind. From this speech, we learn about the transformation in Yaakov’s character in Haran from trying to trick people to being upright and honest. Yaakov had come to Haran after stealing the blessings from Esav, and his stay in Haran was not only to escape from Esav and to find a wife, but also it was a form of redemption for Yaakov. In the speech, Yaakov stressed that he was extremely honest in his work with Lavan even when he was continually being cheated by Lavan.
A possible proof for the insignificance of the terafim is that when Lavan catches up to Yaakov, he gives a speech as to how Yaakov should not have run away, 31:26-30, and then he apparently ends with an acceptance that he has to let Yaakov go since G-d told him not to hurt Yaakov. Only after this concession, Lavan mentions about the terafim, 31:30. Sarna (1989, p. 218) writes that this reference to the terafim at the end of the speech is because “after having emotionally disarmed his opponent by lulling him into a false sense of relief, Lavan then proceeds to deliver the ‘coup de grace’ in the form of the most serious charge of all: theft of his gods.” Sarna’s reading seems backwards to me. After Lavan acquiesced, involuntarily, to Yaakov leaving, the terafim are just an afterthought. The crucial issue for Lavan was Yaakov and his family leaving Lavan and not the terafim as even if Lavan had found the terafim, Yaakov would have left Lavan since Lavan was unable to do anything to Yaakov. Instead, the terafim were just a prop for the reader (and Yaakov’s family?) to learn about Yaakov’s changed work ethic.