Joshua 5:4-6

This is the reason Joshua circumcised them: All the people who came out of Egypt who were males — all the men of war — had died in the wilderness along the way after they had come out of Egypt. Though all the people who came out were circumcised, none of the people born in the wilderness along the way were circumcised after they had come out of Egypt. For the Israelites wandered in the wilderness forty years until all the nation’s men of war who came out of Egypt had died off because they did not obey the LORD. So the LORD vowed never to let them see the land he had sworn to their ancestors to give us, a land flowing with milk and honey.