Genesis 17:19
19 God said, “No, but gSarah your wife shall bear you a son, and you shall call his name hIsaac.1 I will establish my covenant with him as an everlasting covenant for his offspring after him.
Genesis 17:21
21 But lI will establish my covenant with Isaac, mwhom Sarah shall bear to you at this time next year.”
Genesis 21:2
2 And Sarah mconceived and bore Abraham a son in his old age nat the time of which God had spoken to him.
Romans 9:9
9 For this is what the promise said: r“About this time next year I will return, and Sarah shall have a son.”