Does the number forty (40) have any biblical significance?

from the old testament

• The flood account is an example of where the number forty fits into the theme of judgement. God made it rain on the Earth forty days and forty nights (Genesis 7:12) because of  "the wickedness of man" (Genesis 6:5)
• Some Israelite men spent forty days spying out Canaan. Because most of them didn't trust God to conquer the land, the entire nation was punished by having to wander in the wilderness for forty years (Numbers 14:33-34; Deuteronomy 8:2-5).
• Goliath taunted the Israelite army for forty days before David defeated him with God's power (1 Samuel 17:16).
• Not every use of forty points to testing or judgment. For instance, Moses spent forty days and nights on Mt. Sinai receiving the law (Exodus 24:18).

from the new testament

• By far, forty is used much more in the Old Testament than the New Testament. But two important New Testament uses of forty are in the number of days Jesus was tempted by Satan (Matthew 4:2) and the number of days between His resurrection and His ascension (Acts 1:3).
• Other than that, the New Testament only incidentally refers to forty, such as when Hebrews references the Israelites' wandering (Hebrews 3:17) and when Paul refers to the number of lashes he received (2 Corinthians 11:24).

implications for today

People notice patterns. To a gambler, that number he keeps seeing becomes his “lucky” number. He’ll bet that at roulette or play it in the lottery. Wins confirm his belief while any losses are vagaries of the environment (“That woman next to me was wearing an orange shirt—an unlucky color for me!”). But this is problematic. Treating coincidence as meaning and feelings as fact does not ground us in reality.

The same is true with numerology. There is a danger in applying numerology to Scripture. Some numbers are repeated in Scripture, but we should never force meaning onto a passage simply because a common number appears in it. If we do, we turn the Bible into something mystical and manipulatable rather than what it claims to be: the holy, inspired Word of God. In doing so, we unintentionally drift into treating it like a code to crack instead of a message to receive.

Reading Scripture can involve noticing patterns, but those patterns should never outrun the text itself or replace its clear meaning. The goal is not to hunt for hidden signals in numbers but to hear God’s voice in the words He has actually given. What matters most is not what we think we can extract from the structure but what God has already revealed through it.