And these are the generations of Isaac, Abraham's son: Abraham begat Isaac: And Isaac was forty years old when he took Rebekah to wife, the daughter of Bethuel the Syrian of Padanaram, the sister to Laban the Syrian. And Isaac intreated the LORD for his wife, because she was barren: and the LORD was intreated of him, and Rebekah his wife conceived.
Twenty years Rebekah continued barren, for Isaac was 40 years old when he married Rebekah, and 60 years old when Esau and Jacob were born. See Genesis 25:26.