Joshua 5:4 (KJV)

At that time the Lord said unto Joshua, Make thee sharp knives, and circumcise again the children of Israel the second time.

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

And 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.

Now 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 out of Egypt, them they had not circumcised.

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