Charles Ellicott Commentary Genesis 20:2

"And Abraham said of Sarah his wife, She is my sister. And Abimelech king of Gerar sent, and took Sarah." — Genesis 20:2 (ASV)

She is my sister. — Twenty years before, Abraham had acted in the same way in Egypt, and Pharaoh had rebuked him, but sent him away with large presents. We learn from this chapter, Genesis 20:13, that the false representation which twice brought them into trouble was habitual with the two; nor does Abraham ever seem conscious that he was acting in it wrongfully. To us it seems cowardly, in one who had so many men trained to battle, thus to expose his wife to danger; and to have recourse to deceit, at the very time when such abundant revelations were being made to him, also shows an apparent want of faith in God. But Holy Scripture neither represents its heroes as perfect, nor does it raise them disproportionately above the level of their own times.

Its distinguishing feature rather is that it always insists upon a perpetual progress upwards, and urges men onward to be better and holier than those who went before. Abraham was not on the same high spiritual level as a Christian ought to be who has the perfect example of Christ as his pattern, and the gift of the Holy Ghost for his aid; and the fact that God rescued him and Sarah from all danger in Egypt may have seemed to him a warrant that in future difficulties he would have the same Divine protection. Human conduct is always strangely checkered, but we have a wholesome lesson in the fact, that it was Abraham’s shrewd device which twice entangled him in actual danger.

Abimelech (called in Genesis 26:1, king of the Philistines, where see the note) ... took Sarah. — She was now ninety years of age, and naturally her beauty must have faded. Some, however, think that with the promise of a son her youth had been renewed, while others suppose that the purpose uppermost in the mind of Abimelech was political, and that what he really desired was an alliance with the powerful sheikh who had entered his territories.