Genesis 20:3
But God came to Abimelech in a dream by night, and said to him, Behold, thou art but a dead man, for the woman which thou hast taken; for she is a man’s wife. But God came to Abimelech in a dream by night, and said to him, Behold, thou art but a dead man, for the woman which thou hast taken; for she is a man’s wife.
God came to Abimelech in a dream by night to warn him before punishment that for taking Sarah, who was another man's wife, he had come under the sentence of death. He had not yet committed the act, for God restrained him from completing the sin of adultery. Taking another man's wife was already understood as adultery, a great sin against God making the taker guilty and liable to death even when done unwittingly. His coveting of her broke the command against coveting, showing that the principles of the moral law were known from the beginning long before Sinai. The occasion was Abraham's deceptive calling of Sarah his sister a second time from lack of trusting faith in God's protecting care, yet God spoke directly even outside the patriarchal line in divers manners.
Setting and Wording
Genesis 20:3 belongs to Abraham's second deception in calling Sarah his sister, done from lack of trusting faith in God's protecting care and showing his faith was not yet perfect. It is part of the account of Abraham's relations with Abimelech in which unbelief led him to present Sarah his wife as his sister. The same chapter stands as an example of Abraham's lack of truthfulness before Abimelech.
The setting is Abraham's sojourn among the Philistines, where Abimelech had knowledge of the true God and the people showed a higher regard for morality than other nations of Palestine. The account is part of God's providential dealings with the family of Abraham as the chosen progenitor of the promised Seed. It belongs to the history of God's dealing with the Seed and the enemy's attempts to thwart God's plan.
To be called a dead man means to have come under the sentence of death and to be in danger of death, not to have already died. Abimelech was under threat of death because he had taken another man's wife. So the declaration in Genesis 2:17 that Adam would die in the day he ate means he came under the sentence of death that very day.
God warned Abimelech in a dream that taking Sarah, Abraham's wife, made him liable to death. Abimelech himself then served as an instrument of God's stern rebuke to Abraham.
Law Before Sinai
Taking another man's wife was forbidden as adultery long before the law was given to Israel at Sinai. The warning in a dream by night that taking Sarah, Abraham's wife, placed Abimelech under threat of death shows that guilt and mortal danger attached to the act. Even though he acted unwittingly, he was made guilty and liable to dire punishment with death for taking her while she was another man's wife. God directly instructed him that this taking was forbidden, restrained him from committing it, and the account demonstrates that he understood the prohibition. The episode is an example of the seventh commandment being violated before it was proclaimed at Sinai, proving the law forbidding adultery already existed and was known beforehand.
His taking of Abraham's wife came from coveting her, and that coveting violated the command against coveting. This proves the tenth commandment was known before Sinai. That covetousness was idolatry, breaking the first and second commandments.
The principles of God's moral law, including respect for marriage, were known before the law was given at Sinai. The warning not to transgress by taking another man's wife shows that God's commandments made His character and moral requirements known from the beginning. Adultery was therefore regarded as a great sin against God even before Sinai.
Divine Warning and Care
God gave warning before punishment, displaying providential care at work among peoples. The warning came directly to Abimelech concerning the taking of Abraham's wife, showing that God made His will known directly even to those outside the line of the patriarchs. Coming by night in a dream was one of the different ways in which He spoke in times past, illustrating that He spoke at sundry times and in divers manners unto the fathers by the prophets.
The night visit told the king that taking Sarah placed him under threat of death because she was another man's wife, and by that warning God held him back from committing adultery. The guilty are thus warned and restrained before the sin is fully committed. Even in the dark place of unlawful love the Lord is present, so that what in adultery ends in death and despair can become a place of prayer and rescue.