Carl Friedrich Keil and Franz Delitzsch Old Testament Commentary

Abimelech, who had not yet come near her, because God had hindered him by illness (Gen 20:6 and Gen 20:17), excused himself on the ground that he had done no wrong, since he had supposed Sarah to be Abraham's sister, according to both her husband's statement and her own. This plea was admitted by God, who told him that He had kept him from sinning through touching Sarah, and commanded him to restore the woman immediately to her husband, who was a prophet, that he might pray for him and save his life, and threatened him with certain death to himself and all belonging to him in case he should refuse. That Abimelech, when taking the supposed sister of Abraham into his harem, should have thought that he was acting "in innocence of heart and purity of hands," i.e., in perfect innocence, is to be fully accounted for, from his undeveloped moral and religious standpoint, by considering the customs of that day. But that God should have admitted that he had acted "in innocence of heart," and yet should have proceeded at once to tell him that he could only remain alive through the intercession of Abraham, that is to say, through his obtaining forgiveness of a sin that was deserving of death, is a proof that God treated him as capable of deeper moral discernment and piety. The history itself indicates this in the very characteristic variation in the names of God. First of all (Gen 20:3), Elohim (without the article, i.e., Deity generally) appears to him in a dream; but Abimelech recognises the Lord, Adonai, i.e., God (Gen 20:4); whereupon the historian represents האלהים (Elohim with the article), the personal and true God, as speaking to him. The address of God, too, also shows his susceptibility of divine truth. Without further pointing out to him the wrong which he had done in simplicity of heart, in taking the sister of the stranger who had come into his land, for the purpose of increasing his own harem, since he must have been conscious of this himself, God described Abraham as a prophet, whose intercession alone could remove his guilt, to show him the way of salvation. A prophet: lit., the God-addressed or inspired, since the "inward speaking" (Ein-sprache) or inspiration of God constitutes the essence of prophecy. Abraham was προφήτης as the recipient of divine revelation, and was thereby placed in so confidential a relation to God, that he could intercede for sinners, and atone for sins of infirmity through his intercession.