Joshua 5:4-5

5:4 This is why Joshua had to circumcise them: All the men old enough to fight when they left Egypt died on the journey through the desert after they left Egypt. 5:5 Now all the men who left were circumcised, but all the sons born on the journey through the desert after they left Egypt were uncircumcised.

Joshua 5:7

5:7 He replaced them with their sons, whom Joshua circumcised. They were uncircumcised; their fathers had not circumcised them along the way.