Galatians 4:23
Now the son by the servant-woman has his birth after the flesh; but the son by the free woman has his birth through the undertaking of God.
Hebrews 11:11
And by faith Sarah herself had power to give birth, when she was very old, because she had faith in him who gave his word;
Genesis 18:10-14
And he said, I will certainly come back to you in the spring, and Sarah your wife will have a son. And his words came to the ears of Sarah who was at the back of the tent-door.
Genesis 21:1-2
And the Lord came to Sarah as he had said and did to her as he had undertaken.
Romans 9:7-8
And they are not all children because they are the seed of Abraham; but, In Isaac will your seed be named.
Genesis 17:15-19
And God said, As for Sarai, your wife, from now her name will be not Sarai, but Sarah.
Romans 4:18-21
Who without reason for hope, in faith went on hoping, so that he became the father of a number of nations, as it had been said, So will your seed be.
Romans 10:8
But what does it say? The word is near you, in your mouth and in your heart: that is, the word of faith of which we are the preachers:
Galatians 4:28-29
Now we, brothers, as Isaac was, are the children of the undertaking of God.