Genesis 17:19
17:19 God said, “No, Sarah your wife is going to bear you a son, and you will name him Isaac. I will confirm my covenant with him as a perpetual covenant for his descendants after him.
Genesis 17:21
17:21 But I will establish my covenant with Isaac, whom Sarah will bear to you at this set time next year.”
Romans 9:7-8
9:7 nor are all the children Abraham’s true descendants; rather “
through Isaac will your descendants be counted.”
9:8 This means
it is not the children of the flesh
who are the children of God; rather, the children of promise are counted as descendants.
Hebrews 11:18
11:18 God had told him, “
Through Isaac descendants will carry on your name,”