I will certainly return - Abraham was now ninety-nine years of age, and this promise was fulfilled when he was a hundred; so that the phrase according to the time of life must mean either a complete year, or nine months from the present time, the ordinary time of pregnancy. Taken in this latter sense, Abraham was now in the ninety-ninth year of his age, and Isaac was born when he was in his hundredth year.

And he said,.... The same that put the question, Jehovah himself, as appears by what follows:

I will certainly return unto thee according to the time of life; not by a personal appearance as now, but by the fulfilment of his promise which he had before given to Abraham, that he should have a son by Sarah, and now renews it; and this would be about the same time in the next year, perhaps at the spring of the year, which may be called "a time of life", when all things revive, which in the winter season seem to be dead; a fit emblem this of the case and condition of Abraham and Sarah, both as they now were, and afterwards would be; for, though their bodies were as it were dead and unfit for generation, yet nature would revive in them again: unless it be understood of the whole time of the conception, quickening, and birth of an infant, at the usual time a woman goes with child, which is nine months, when the infant is a perfect living child. All the Targums paraphrase it,"in which ye shall be alive,''safe and well, and so most of the Jewish commentators; as if it was a promise to Abraham and Sarah, that they should live to see the promise made good next given; but this seems not so agreeable as either of the former, see 2 Kings 4:16,

and, lo, Sarah thy wife shall have a son; it was by degrees that this was made known to Abraham; first he was told he should have a son, but it was not said by whom he should have it; some years after that he is informed he should have a son by Sarah, but not when; but now it is revealed to him, that he should have one by her the next year:

and Sarah heard it in the tent door, which was behind him; or, "and it was behind him" (u); that is, the tent door was at the back of the person speaking; Sarah, hearing her name mentioned, got to the tent door to listen to what might be further said; and the place where she was, was behind the speaker, who stood between her and Abraham, with whom he was conversing; Abraham was before high, and Sarah behind him, so that he could not see her when she laughed, and yet he knew she did; and for the sake of that, this circumstance is remarked: both the Targums of Jonathan and Jerusalem paraphrase the clause,"and Ishmael stood behind it,''the tent door; and the former adds, and hearkened to what the angel said.

(u) "et ipsum post eum", Montanus.

And he said, I will certainly return unto thee according to the time of {f} life; and, lo, Sarah thy wife shall have a son. And Sarah heard it in the tent door, which was behind him.

(f) That is, about this time when she shall be alive, or when the child shall come into this life.

18:10 I will certainly return unto thee - And visit thee. God will return to those that bid him welcome.

10. Sarah heard it in the tent door, which was behind him-The women's apartment is in the back of the tent, divided by a thin partition from the men's.

18:9-15 Where is Sarah thy wife? was asked. Note the answer, In the tent. Just at hand, in her proper place, occupied in her household concerns. There is nothing got by gadding. Those are most likely to receive comfort from God and his promises, who are in their proper place, and in the way of their duty, Lu 2:8. We are slow of heart to believe, and need line upon line to the same purport. The blessings others have from common providence, believers have from the Divine promise, which makes them very sweet, and very sure. The spiritual seed of Abraham owe their life, and joy, and hope, and all, to the promise. Sarah thinks this too good news to be true; she laughed, and therefore cannot as yet find in her heart to believe it. Sarah laughed. We might not have thought there was a difference between Sarah's laughter and Abraham's, ch. 17:17; but He who searches the heart, saw that the one sprung from unbelief, and the other from faith. She denied that she had laughed. One sin commonly brings in another, and it is not likely we shall strictly keep to truth, when we question the Divine truth. But whom the Lord loves he will rebuke, convict, silence, and bring to repentance, and if they sin before him.