(17) Abraham . . . laughed.--The Jewish interpreters regard Abraham's laugh as one of joy, and Sarah's (Genesis 18:12) as one of unbelief. We may, however, well doubt whether there really was this difference between them; but our Lord confirms the View that joy was uppermost in Abraham's heart (John 8:56). Still with belief there was surprise, and the feeling that what was promised was so strange as to be well-nigh incredible. One who was ready to sacrifice his only son at God's word (Hebrews 11:19) would not be staggered by this strangeness, and yet the thought of Sarah's bearing a child at the age of ninety might easily present itself to his mind in a ludicrous aspect. As for Sarah, there is no proof that at the time when she laughed she knew or even suspected that the three travellers were more than men. She overheard their conversation, and laughed, imagining perhaps that they did not know how old she was. Really, the idea brought out by this double laughter is that Isaac's birth was contrary to nature.

Verse 17. - Then Abraham fell upon his face (vide Ver. 3), and laughed. וַיּצְחָק from צָחַק, to laugh. Cf. καχάζω καγχάζω, cachin-nor, German, kichern; καὶ ἀγέλασε (LXX.); rejoiced (Onkelos); marveled (Jerome, Targums); laughed for joy (Arabic version, Augustine, Calvin, Delitzsch, Keil, Murphy, et alii); not a smile of incredulity (Jerome, Chrysostom) or of diffidence (Kalisch), as partitionists assert in order to produce a contradiction between the Elohist and Jehovist of Genesis 15. And said in his heart, Shall a child be born unto him that is (literally, to the son of) an hundred years old? A suggestion of natural reason which was overruled by faith (Calvin, Wordsworth), though better regarded as the exclamation of holy wonder, or as an illustration of believing not for joy (Inglis; cf. Luke 24:41). And shall Sarah, that is ninety years old, bear? Yes. What reason declared impossible was possible to faith. "He considered not the deadness of Sarah s womb" (Romans 4:19).

17:15-22 Here is the promise made to Abraham of a son by Sarai, in whom the promise made to him should be fulfilled. The assurance of this promise was the change of Sarai's name into Sarah. Sarai signifies my princess, as if her honour were confined to one family only; Sarah signifies a princess. The more favours God confers upon us, the more low we should be in our own eyes. Abraham showed great joy; he laughed, it was a laughter of delight, not of distrust. Now it was that Abraham rejoiced to see Christ's day; now he saw it and was glad, Joh 8:56. Abraham, dreading lest Ishmael should be abandoned and forsaken of God, put up a petition on his behalf. God gives us leave in prayer to be particular in making known our requests. Whatever is our care and fear, should be spread before God in prayer. It is the duty of parents to pray for their children, and the great thing we should desire is, that they may be kept in covenant with Him, and may have grace to walk before him in uprightness. Common blessings are secured to Ishmael. Outward good things are often given to those children of godly parents who are born after the flesh, for their parents' sake. Covenant blessings are reserved for Isaac, and appropriated to him.Then Abraham fell upon his face,.... In reverence of the divine Being, and as amazed at what was told him:

and laughed; not through distrust and diffidence of the promise, as Sarah did, for he staggered not at that through unbelief, but for joy at such good news; and so Onkelos renders it, "and he rejoiced", with the joy of faith; it may be our Lord refers to this in John 8:56; he saw Christ in the promise of Isaac, and rejoiced that he should spring from his seed: the Targums of Jonathan and Jerusalem paraphrase it, "and he wondered"; he was amazed at the grace of God that gave him such a promise, and he was astonished at the power of God that must be exerted in the fulfilment of it: and therefore it follows:

and said in his heart; within himself, without expressing anything as to be heard and understood by any creature; but the omniscient God knew what he said, and the language of it, whether of unbelief or not:

shall a child be born unto him that is an hundred years old? not that he was now a full an hundred years old, he was ninety nine, and going in his hundredth year; but then he would be, as he was, an hundred years old when this child was born to him, Genesis 21:5. It had been no unusual thing for a child to be born to a man when an hundred, and even many hundred years old, but it was so in Abraham's time; though indeed after this we read that Abraham himself had six sons by Keturah, when, his natural strength was afresh invigorated, and his youth was renewed like the eagle's; and besides Abraham said this, not so much with respect to himself, though his age was a circumstance that served to heighten the wonder, as with respect to Sarah, and the circumstances in which she was, who was to bear this son to him:

and shall Sarah, that is ninety years old, bear? and with whom it had ceased to be after the manner of women, which made it more difficult of belief how it could be. Some think that Abraham said this, as somewhat doubting of it, until he was more strongly assured by the Lord that so it would be indeed, as is expressed in Genesis 17:19; but meeting with no reproof for what he said and did, as Sarah, it seems to show the contrary.