'Forty Years' in the Bible

Kenan lived after he became the father of Mahalalel eight hundred forty years, and became the father of sons and daughters

Isaac was forty years old when he took Rebekah, the daughter of Bethuel the Syrian of Paddan Aram, the sister of Laban the Syrian, to be his wife.

When Esau was forty years old, he took as wife Judith, the daughter of Beeri the Hittite, and Basemath, the daughter of Elon the Hittite.