It’s our 400th post! In most religions originating in the Middle East, the number 40 equals a large unspecific number: 40 days, 40 nights, 40 years should all be interpreted as “many” days, nights, or years.

Hey, this is the 400th regular post on this website (not counting update posts). Thanks for reading!
The number 40 is a rather odd one. While today we understand it as a precise figure, historically it has often been used as a generic large number, closer to our sense of “lots” or “many.”
Take Judaism and Christianity, for example. In the Great Flood the rain lasted forty days and forty nights. After the exodus from Egypt, the Israelites wandered the wilderness for forty years. Moses spent forty days and forty nights on Mount Sinai (on three separate occasions, actually). Saul, David, and Solomon all ruled for forty years. Jesus was tempted by the devil for forty days and forty nights, and there were forty days between his resurrection and his ascension into heaven.
Wandering the wilderness and Moses on Mount Sinai also feature in Islam, of course. Additionally, Al-Masih ad-Dajjal (the prophesied one-eyed false Messiah, doppelgänger of Jesus) will walk the Earth for forty days – although apparently of those days “one [will be] like a year, one like a month, one like a week, and rest of his days like yours.” I don’t quite know what that means.
Forty has survived as a generically large number in phrases like “forty winks,” but why is it such a prominent number in Abrahamic religions? Well, forty happens to be the sacred number of Enki, the Sumerian god known as the Lord of the Earth, so it’s possible that all of the later religions borrowed that numeral for their own purposes. Much like they borrowed the Great Flood – which first appeared in Akkadian or Sumerian mythology nearly four thousand years ago.