Genesis 17:15-22
God fulfills His promises through His appointed means, not human alternatives.
15 God said to Abraham, “As for Sarai your wife, you shall not call her name Sarai, but her name will be Sarah.
16 I will bless her, and moreover I will give you a son by her. Yes, I will bless her, and she will be a mother of nations. Kings of peoples will come from her.”
17 Then Abraham fell on his face, and laughed, and said in his heart, “Will a child be born to him who is one hundred years old? Will Sarah, who is ninety years old, give birth?”
18 Abraham said to God, “Oh that Ishmael might live before you!”
19 God said, “No, but Sarah, your wife, will bear you a son. You shall call his name Isaac. I will establish my covenant with him for an everlasting covenant for his offspring after him.
20 As for Ishmael, I have heard you. Behold, I have blessed him, and will make him fruitful, and will multiply him exceedingly. He will become the father of twelve princes, and I will make him a great nation.
21 But I will establish my covenant with Isaac, whom Sarah will bear to you at this set time next year.”
22 When he finished talking with him, God went up from Abraham.
God fulfills His promises through His appointed means, not human alternatives.
To reveal that the covenant promise will be fulfilled through Sarah’s son Isaac, not through Ishmael, and to establish God’s sovereign choice in covenant fulfillment.
God Reaffirms His Covenant, Renames Abram and Sarai, and Appoints Circumcision as the Covenant Sign
God sovereignly reaffirms and defines His covenant with Abraham by promising miraculous offspring through Sarah, appointing circumcision as the covenant sign, and calling Abraham to covenant faithfulness before the God who will accomplish what He has promised.