Question: A pastor from a small Florida town requested the Jewish explanation of the obscure term "kesut einayim" in Genesis 20:16. He also wanted an explanation of how 1,000 pieces of silver could clear Sarah's reputation, and what was its significance in the context of ancient Near Eastern law and custom.
Answer: Although this term is often translated as "vindication", its literal meaning is "covering of the eyes."
Nahum Sarna's The JPS Torah Commentary: Genesis (1989) provides a succinct summary of the literal and figurative meanings of this phrase (p. 144). The ArtScroll Tanach Series commentary on Genesis by Zlotowitz provides a variety of explanations by a range of classical rabbinic commentators. For example:
According to Rashbam, the 1,000 pieces of silver refers to the dowry Abimelech gave Abraham (Sarah's supposed brother) demonstrating Abimelech's honorable intention to legally marry Sarah. Regarding "kesut einayim" Rashi says "The gifts I have given to you will serve to close the eyes of all those who would otherwise have regarded you contemptuously" (Artscroll p. 738)--again emphasizing Abimelech's honorable intentions, the restoration of Sarah's honor and the removal of any disgrace. R' Bachya and Rav Yehudah bar Ilia emphasize the literal meaning of "kesut": a garment. Sarah should wear a garment which will distract the public from noticing her beauty, or a veil which will actually hide Sarah from public view.
Sarna refers us to Moshe Weinfeld's article "Sarah and Abimelech (Genesis 20) Against the Background of an Assyrian Law and the Genesis Apocryphon" in Mélanges Bibliques et Orientaux en l’Honneur de M. Mathias Delcor (1985). Weinfeld demonstrates how a text of Genesis Apocryphon found at Qumran partially verifies Cassuto's 1944 hypothesis that that the transfer of money from Abimelech to Abraham was a standard legal practice in the Middle East in such situations. This Qumran text includes an additional detail in the Abraham/Sarah/Abimelech narrative, which is absent in the Biblical text. An oath is uttered by Abimelech.
Weinfeld quotes a translation of Middle Assyrian Laws: “a man who takes a married woman on a . . . journey with him, without knowing that she is married, must make an oath to that effect [that he did not know she was married] and give two talents of tin to the woman’s husband (Middle Assyrian Laws, I, sect. 22)” p. 431. Weinfeld's conclusion: “we can assume that we have here a practice widespread over the ancient Near East for a period of more than a thousand years.” p. 432