Joshua 5:3-6

³And Joshua made him sharp knives, and circumcised the children of Israel at the hill of the foreskins.

⁴And this is the cause why Joshua did circumcise: All the people that came out of Egypt, that were males, even all the men of war died in the wilderness by the way, after they came out of Egypt.

⁵Now all the people that came out were circumcised; but all the people that were born in the wilderness by the way as they came forth from Egypt, them they had not circumcised.

⁶For the children of Israel walked forty years in the wilderness, till all the people that were men of war who came out of Egypt were consumed, because they obeyed not the voice of the LORD: to whom the LORD swore that he would not show them the land which the LORD swore to their fathers that he would give us, a land that floweth with milk and honey.