'Forty Years' in the Bible

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

and Isaac was forty years old when he took Rebekah, the daughter of Bethuel the Aramean of Paddan-aram, the sister of Laban the Aramean, to be his wife.

When Esau was forty years old he married Judith the daughter of Beeri the Hittite, and Basemath the daughter of Elon the Hittite;