Joshua 5:2-5

2The Lord said to Joshua at that time, ‘Make knives of stone and circumcise the Israelite men.’

3So Joshua made the knives and he circumcised the men at Gibeath Haaraloth.

4This is why Joshua had to circumcise them: All the men who were old enough to fight when they came out of Egypt had now died. They died in the desert as they travelled to Canaan.

5All those men who came out of Egypt had already been circumcised. But all the sons who were born on the journey through the desert had not been circumcised.