Genesis 20:2

And Abraham said of Sarah his wife, She is my sister: and Abimelech king of Gerar sent, and took Sarah.

Abraham fearfully concealed his marriage by calling Sarah his sister, and Abimelech king of Gerar took her on that word. Taking another man's wife would have been adultery and great guilt bringing punishment on Abimelech and his kingdom, though done unwittingly, so God restrained him from that sin against Himself. Abimelech already knew this taking was forbidden, proving the seventh commandment and the moral law were known and binding long before Sinai. The deception also shows Abraham's faith was not yet perfect, for even he staggered in trusting God's protecting care to fulfill the promise.

Narrative Setting and Outcome

Abimelech, meaning my father the king, was the name of the Philistine king of Gerar who took Sarah after Abraham said she was his sister, and it was a name common to Philistine kings. The verse belongs to the Genesis 12 to 26 account of God's providential dealings with the family of Abraham as the chosen progenitor of the Seed, continuing the story of God's dealing with the Seed. The account is Abraham's stay among the Philistines, presenting Abimelech as knowing the true God and the Philistines as having a higher regard for morality than the other nations of Palestine.

The verse records the second time Abraham deceptively said Sarah was his sister rather than his wife. He acted from fearfulness and failed to tell the truth before Abimelech. His deception came from lack of trusting faith in God's protecting care, showing his faith was not yet perfect at that stage of his growth, and it belonged to his attempt to secure God's promise through human planning rather than trusting God's plan.

Abraham's deception became the occasion for a stern rebuke from Abimelech. The account of Abimelech and Sarah ended with Abimelech sending Abraham's household on its way with rich gifts and goodwill. Abraham's large household was in this presented as a God-blessed patriarchal family school.

Law Known Before Sinai

Taking Sarah would have been adultery and sin against God, bringing great sin and guiltiness with dire punishment upon Abimelech and his kingdom. It was done unwittingly because Abraham said she was his sister, yet it would still have brought that punishment, so God withheld and restrained Abimelech from committing that sin. Abimelech knew that taking another man's wife was forbidden and recognized it as sin against God, being directly instructed by God about this prohibition.

The verse therefore proves that sin, guilt, and the law defining them, especially the seventh commandment against adultery and the moral law generally, were known and understood long before Sinai. The absence of a recorded express prohibition of adultery for Adam or the patriarchs does not prove the law was not binding, and the same holds for the Sabbath, whose principles like all ten commandments were clearly understood from the beginning. Abimelech's taking of Sarah also violated the tenth commandment, for he coveted Abraham's wife and therefore took her for himself, showing that commandment was known and violated before Sinai. Such covetousness is idolatry that breaks the first and second commandments. Abraham's claim that Sarah was his sister is itself an instance of violating the seventh and ninth commandments before the law was proclaimed at Sinai.

Taking a married woman goes down into the hell of adulterous guilt, despair, and remorse. Yet God is in that place to warn, to restrain from sin, and to lift up and save the soul who cries out to Him.

Faith Tested and Applied

Abraham saying of Sarah his wife that she was his sister was the second time he said she was his wife's sister rather than his wife, a deception done from lack of trusting faith in God's protecting care, showing that his faith was not yet perfect at that stage of his growth in faith. His lack of trust led him to present Sarah his wife as his sister, illustrating that even a believer known for faith does not always trust God fully. The saying that Sarah was his sister, after which Abimelech king of Gerar took her, belongs to the account of Abraham's trials of faith and shows that he did not immediately attain fullness of faith, but the lesson of faith came to him repeatedly. His asking Sarah to conceal that she was his wife was one time he staggered rather than fully trusting God. His getting into trouble by calling Sarah his sister while she was his wife stands as a cautionary example bearing on how spouses speak of one another.