Genesis 11:30 reveals Sarai's barrenness — the very condition that makes her bearing a son in old age so remarkable here. It provides the backstory.

Genesis 17:15-19 records God's specific promise that Sarah would bear a son. The servant's report echoes this fulfilled prophecy — a son born to Sarah in old age.

Genesis 18:10-14 records the Lord reaffirming the promise and Sarah's laughter. Her bearing Isaac in old age fulfills exactly what was promised there.

Genesis 21:1-7 narrates the actual birth of Isaac to aged Sarah. The servant's report here directly references that event as proof of God's blessing.

In Genesis 25:5, the narrative confirms what the servant reports here: Abraham gave all he had to Isaac. The servant's testimony matches the narrator's later summary.

Romans 4:19 describes Abraham not weakening in faith despite Sarah's barrenness and their aged bodies — the very circumstances that made Isaac's birth miraculous.