Joshua 5:2-5

2At that time Jehovah said unto Joshua, Make thee knives of flint, and circumcise again the children of Israel the second time. 3And Joshua made him knives of flint, 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 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. 5For 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, they had not circumcised.