Biblical Commentary on the Old Testament, by Carl Friedrich Keil and Franz Delitzsh, [1857-78], at sacred-texts.com
After the destruction of Sodom and Gomorrah, Abraham removed from the grove of Mamre at Hebron to the south country, hardly from the same fear as that which led Lot from Zoar, but probably to seek for better pasture. Here he dwelt between Kadesh (Gen 14:7) and Shur (Gen 16:7), and remained for some time in Gerar, a place the name of which has been preserved in the deep and broad Wady Jurf el Gerr (i.e., torrent of Gerar) about eight miles S.S.E. of Gaza, near to which Rowland discovered the ruins of an ancient town bearing the name of Khirbet el Gerr. Here Abimelech, the Philistine king of Gerar, like Pharaoh in Egypt, took Sarah, whom Abraham had again announced to be his sister, into his harem, - not indeed because he was charmed with the beauty of the woman of 90, which was either renovated, or had not yet faded (Kurtz), but in all probability "to ally himself with Abraham, the rich nomad prince" (Delitzsch). From this danger, into which the untruthful statement of both her husband and herself had brought her, she was once more rescued by the faithfulness of the covenant God. In a dream by night God appeared to Abimelech, and threatened him with death (מת הנּך en te moriturum) on account of the woman, whom he had taken, because she was married to a husband.
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.
Abimelech carried out the divine instructions. The next morning he collected his servants together and related what had occurred, at which the men were greatly alarmed. He then sent for Abraham, and complained most bitterly of his conduct, by which he had brought a great sin upon him and his kingdom.
"What sawest thou," i.e., what hadst thou in thine eye, with thine act (thy false statement)? Abimelech did this publicly in the presence of his servants, partly for his own justification in the sight of his dependents, and partly to put Abraham to shame. The latter had but two weak excuses: (1) that he supposed there was no fear of God at all in the land, and trembled for his life because of his wife; and (2) that when he left his father's house, he had arranged with his wife that in every foreign place she was to call herself his sister, as she really was his half-sister. On the subject of his emigration, he expressed himself indefinitely and with reserve, accommodating himself to the polytheistic standpoint of the Philistine king: "when God (or the gods, Elohim) caused me to wander," i.e., led me to commence an unsettled life in a foreign land; and saying nothing about Jehovah, and the object of his wandering as revealed by Him.
Abimelech then gave him back his wife with a liberal present of cattle and slaves, and gave him leave to dwell wherever he pleased in his land. To Sarah he said, "Behold, I have given a thousand shekele of silver to thy brother; behold, it is to thee a covering of the eyes (i.e., an expiatory gift) with regard to all that are with thee ("because in a mistress the whole family is disgraced," Del.), and with all - so art thou justified." The thousand shekels (about 131) were not a special present made to Sarah, but indicate the value of the present made to Abraham, the amount of which may be estimated by this standard, that at a later date (Exo 21:32) a slave was reckoned at 30 shekels. By the "covering of the eyes" we are not to understand a veil, which Sarah was to procure for 1000 shekels; but it is a figurative expression for an atoning gift, and is to be explained by the analogy of the phrase פּני פ כּפּר "to cover any one's face," so that he may forget a wrong done (cf. Gen 32:21; and Job 9:24, "he covereth the faces of the judges," i.e., he bribes them). ונוכחת can only be the 2 pers. fem. sing. perf. Niphal, although the Dagesh lene is wanting in the ת; for the rules of syntax will hardly allow us to regard this form as a participle, unless we imagine the extremely harsh ellipsis of נוכחת for אתּ נוכחת. The literal meaning is "so thou art judged," i.e., justice has been done thee.
After this reparation, God healed Abimelech at Abraham's intercession; also his wife and maids, so that they could bear again, for Jehovah had closed up every womb in Abimelech's house on Sarah's account. אמהות, maids whom the king kept as concubines, are to be distinguished from שׁפחות female slaves (Gen 20:14). That there was a material difference between them, is proved by Sa1 25:41. כּל־רחם עצר כּל does not mean, as is frequently supposed, to prevent actual childbirth, but to prevent conception, i.e., to produce barrenness (Sa1 1:5-6). This is evident from the expression "He hath restrained me from bearing" in Gen 16:2 (cf. Isa 66:9, and Sa1 21:6), and from the opposite phrase, "open the womb," so as to facilitate conception (Gen 29:31, and Gen 30:22). The plague brought upon Abimelech's house, therefore, consisted of some disease which rendered the begetting of children (the coitus) impossible. This might have occurred as soon as Sarah was taken into the royal harem, and therefore need not presuppose any lengthened stay there. There is no necessity, therefore, to restrict ויּלדוּ to the women and regard it as equivalent to ותּלדנה, which would be grammatically inadmissible; for it may refer to Abimelech also, since ילד signifies to beget as well as to bear. We may adopt Knobel's explanation, therefore, though without approving of the inference that Gen 20:18 was an appendix of the Jehovist, and arose from a misunderstanding of the word ויּלדוּ in Gen 20:17. A later addition Gen 20:18 cannot be; for the simple reason, that without the explanation give there, the previous verse would be unintelligible, so that it cannot have been wanting in any of the accounts. The name Jehovah, in contrast with Elohim and Ha-Elohim in Gen 20:17, is obviously significant. The cure of Abimelech and his wives belonged to the Deity (Elohim). Abraham directed his intercession not to Elohim, an indefinite and unknown God, but to האלהים; for the God, whose prophet he was, was the personal and true God. It was He too who had brought the disease upon Abimelech and his house, not as Elohim or Ha-Elohim, but as Jehovah, the God of salvation; for His design therein was to prevent the disturbance of frustration of His saving design, and the birth of the promised son from Sarah.
But if the divine names Elohim and Ha-Elohim indicate the true relation of God to Abimelech, and here also it was Jehovah who interposed for Abraham and preserved the mother of the promised seed, our narrative cannot be merely an Elohistic side-piece appended to the Jehovistic account in Gen 12:14., and founded upon a fictitious legend. The thoroughly distinctive character of this event is a decisive proof of the fallacy of any such critical conjecture. Apart from the one point of agreement-the taking of Abraham's wife into the royal harem, because he said she was his sister in the hope of thereby saving his own life (an event, the repetition of which in the space of 24 years is by no means startling, when we consider the customs of the age) - all the more minute details are entirely different in the two cases. In king Abimelech we meet with a totally different character from that of Pharaoh. We see in him a heathen imbued with a moral consciousness of right, and open to receive divine revelation, of which there is not the slightest trace in the king of Egypt. And Abraham, in spite of his natural weakness, and the consequent confusion which he manifested in the presence of the pious heathen, was exalted by the compassionate grace of God to the position of His own friend, so that even the heathen king, who seems to have been in the right in this instance, was compelled to bend before him and to seek the removal of the divine punishment, which had fallen upon him and his house, through the medium of his intercession. In this way God proved to the Philistine king, on the one hand, that He suffers no harm to befall His prophets (Psa 105:15), and to Abraham, on the other, that He can maintain His covenant and secure the realization of His promise against all opposition from the sinful desires of earthly potentates. It was in this respect that the event possessed a typical significance in relation to the future attitude of Israel towards surrounding nations.