Joshua 5:4, 6

And this is the cause why Joshua did circumcise: all the people that came forth out of Egypt, that were males, even all the men of war, died in the wilderness by the way, after they came forth out of Egypt.

For the children of Israel walked forty years in the wilderness, till all the nation, even the men of war that came forth out of Egypt, were consumed, because they hearkened not unto the voice of Jehovah: unto whom Jehovah sware that he would not let them see the land which Jehovah sware unto their fathers that he would give us, a land flowing with milk and honey.