Genesis 20:2

She is my sister. Although Abraham lived in peace and security wherever he had previously pitched his tent in the land of Canaan, he seems to have mistrusted the king of Gerar, a Philistine prince (see on ch. 21:32). It is paradoxical to find one who had defeated the combined expeditionary forces of four Mesopotamian powers suddenly cowering in mortal fear before a single city prince. It is even more puzzling to discover Abraham, that paragon of faith, abruptly reverting to the very ruse that had brought him so much embarrassment and anxiety in Egypt (see ch. 12:10-20). After the many evidences of the power and protection of God he had witnessed, another dismal failure of faith such as this is strange indeed. Some 20 years had passed since that former mistake, and it may be that time had erased the impression then made.

Abimelech. The name Abimelech, “my father the king,” may in reality have been a Philistine title like that of Pharaoh in Egypt, instead of a proper name. The king of Gerar in Isaac’s time is called Abimelech (ch. 26:8), as is also King Achish of Gath in David’s time (1 Sam. 21:10; cf. Ps. 34, title). The ruler of Gerar seems to have taken into his harem all the unmarried women of this domain who captured his fancy. Even more so than 25 years earlier, it seems strange that Sarah, at the age of 90, was still so attractive as to be desired by a Palestinian prince. To be sure, nearly 40 years of her life still remained. Abimelech may also have intended this marriage to seal an alliance between himself and Abraham. He apparently felt the presence of Abraham a benefit to him (see ch. 20:15).