According to rabbinical tradition, forty represents the time it takes for something to move from beginning to fulfillment or completion. This number occurs many times in the sacred stories of all three Abrahamic faiths: Judaism, Christianity, and Islam.
Carried to term
We drift in amniotic waters forty weeks before
we are ready to be born. We floated forty years
in Sinai dust, an embryonic people in a desert
womb. Forty, the number of completion: forty
years — a lifetime — before we were ready
to break the waters of the Jordan and enter
the world something new, as a people
delivered by God.
The Daily Compost 