Genesis 20:11, commentary and pictures

The verse belongs to Abraham's sojourn among the Philistines in Gerar and gives his explanation for calling Sarah his sister, that he thought surely the fear of God was not in that place and they would slay him for his wife's sake. His judgment about the place led him to act from fear, becoming untruthful and deceptive toward Abimelech. The deception showed faith that was not yet perfect, a distrust of God and want of trusting faith in God's protecting care, one of two such failures when unbelief led him to present Sarah as his sister.

Abimelech knew the true God, understood that adultery is forbidden, was directly instructed by God about it, and showed that knowledge by his fear and by restoring Sarah. His dealings with Abraham served as a stern rebuke to him. In this account the Philistines showed a higher regard for morality than the other nations of Palestine.

The verse is evidence that people before Moses knew moral principles through God's moral law, including the duty to respect human life. It assumes that taking another man's wife is a sin that the fear of God forbids, showing the duty enforced by the seventh commandment and the sacredness of marriage were known and binding before the Ten Commandments were given. That sacredness did not begin with the Decalogue, which only guards an institution made for man before the fall. Abraham's account about Sarah is an instance of the ninth commandment being violated before the law was proclaimed at Sinai, showing that commandment was already known.