Genesis 17:15

The appointment of the sign of the covenant was followed by this further revelation as to the promised seed, that Abram would receive it through his wife Sarai. In confirmation of this her exalted destiny, she was no longer to be called Sarai (שׂרי, probably from שׂרר with the termination ai, the princely), but שׂרה, the princess; for she was to become nations, the mother of kings of nations. Abraham then fell upon his face and laughed, saying in himself (i.e., thinking), "Shall a child be born to him that is a hundred years old, or shall Sarah, that is ninety years old, bear?" "The promise was so immensely great, that he sank in adoration to the ground, and so immensely paradoxical, that he could not help laughing" (Del.). "Not that he either ridiculed the promise of God, or treated it as a fable, or rejected it altogether; but, as often happens when things occur which are least expected, partly lifted up with joy, partly carried out of himself with wonder, he burst out into laughter" (Calvin). In this joyous amazement he said to God (Gen 17:18), "O that Ishmael might live before Thee!" To regard these words, with Calvin and others, as intimating that he should be satisfied with the prosperity of Ishmael, as though he durst not hope for anything higher, is hardly sufficient. The prayer implies anxiety, lest Ishmael should have no part in the blessings of the covenant. God answers, "Yes (אבל imo), Sarah thy wife bears thee a son, and thou wilt call his name Isaac (according to the Greek form Ἰσαάκ, for the Hebrew יצחק, i.e., laughter, with reference to Abraham's laughing; Gen 17:17, cf. Gen 21:6), and I will establish My covenant with him," i.e., make him the recipient of the covenant grace. And the prayer for Ishmael God would also grant: He would make him very fruit…

Here is, I. The promise made to Abraham of a son by Sarai, that son in whom the promise made to him should be fulfilled, that he should be the father of many nations; for she also shall be a mother of nations, and kings of people shall be of her, Gen 17:16. Note, 1. God reveals the purposes of his good-will to his people by degrees. God had told Abraham long before that he should have a son, but never till now that he should have a son by Sarai. 2. The blessing of the Lord makes fruitful, and adds no sorrow with it, no such sorrow as was in Hagar's case. "I will bless her with the blessing of fruitfulness, and then thou shalt have a son of her." 3. Civil government and order are a great blessing to the church. It is promised, not only that people, but kings of people, should be of her; not a headless rout, but a well-modelled well-governed society. II. The ratification of this promise was the change of Sarai's name into Sarah (Gen 17:15), the same letter being added to her name that was to Abraham's, and for the same reasons. Sarai signifies my princess, as if her honour were confined to one family only. Sarah signifies a princess - namely, of multitudes, or signifying that from her should come the Messiah the prince, even the prince of the kings of the earth. III. Abraham's joyful, thankful, entertainment of this gracious promise, Gen 17:17. Upon this occasion he expressed, 1. Great humility: He fell on his face. Note, The more honours and favours God confers upon us the lower we should be in our own eyes, and the more reverent and submissive before God. 2. Great joy: He laughed. It was a laughter of delight, not of distrust. Note, Even the promises of a holy God, as well as his performances, are the joys of holy souls; there is the joy of faith as well as the joy of f…

17:15-16 Sarah: The new name, fitting for one who would be the mother of kings, was a milestone in Sarah’s calling and brought attention to the promise.