So Abraham prayed. In two respects the wonderful favor of God towards Abraham was apparent; firsts that, with outstretched hand, He avenged the injury done to him; and, secondly, that, through Abraham's prayer, He became pacified towards the house of Abimelech. It was necessary to declare, that the house of Abimelech had been healed in answer to Abraham's prayers; in order that, by such a benefit, the inhabitants might be the more closely bound to him. A question, however, may be agitated respecting the kind of punishment described in the expression, the whole house was barren. For if Abraham had gone into the land of Gerar, after Sarah had conceived, and if the whole of what Moses has here related was fulfilled before Isaac was born, how was it possible that, in so short a time, this sterility should be manifest? If we should say, that the judgment of God was then made plain, in a manner to us unknown, the answer would not be inappropriate. Yet I am not certain, that the series of the history has not been inverted. The more probable supposition may seem to be, that Abraham had already been resident in Gerar, when Isaac was promised to him; but that the part, which had before been omitted, is now inserted by Moses. Should any one object, that Abraham dwelt in Mamre till the destruction of Sodom, there would be nothing absurd in the belief, that what Moses here relates had taken place previously. Yet, since the correct notation of time does little for the confirmation of our faith, I leave both opinions undecided.

So Abraham prayed - This was the prime office of the נביא nabi; see Genesis 20:7.

So Abraham prayed unto God,.... As the Lord had told Abimelech be would, Genesis 20:7; he might pray for the forgiveness of him and his wife, and might give thanks that Sarah had been restored to him; but chiefly it was on account of Abimelech and his family:
and God healed Abimelech, and his wife, and his maidservants: who by reason of some disease were rendered unfit for and incapable of cohabitation with their husbands, and they with them; but upon Abraham's prayer for them, who was heard, they were healed, and the disorder removed; the Targum of Jonathan is,"his wife and concubines;"
and they bare children; cohabited and conceived, and bare and brought forth children, all which are comprehended in this expression.

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 (Genesis 20:14). That there was a material difference between them, is proved by 1-Samuel 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 (1-Samuel 1:5-6). This is evident from the expression "He hath restrained me from bearing" in Genesis 16:2 (cf. Isaiah 66:9, and 1-Samuel 21:6), and from the opposite phrase, "open the womb," so as to facilitate conception (Genesis 29:31, and Genesis 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 Genesis 20:18 was an appendix of the Jehovist, and arose from a misunderstanding of the word ויּלדוּ in Genesis 20:17. A later addition Genesis 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 Genesis 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 Genesis 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 (Psalm 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.