Joshua 5:7

And the children [whom] he raised up in their stead, them
Joshua circumcised
Who were born to them in the wilderness, and succeeded them, some of which might be near forty years of age; as for those that were born before, of which there might be many now living, they had been circumcised already, but others, were not:

for they were circumcised, because they had not circumcised them by
the way;
or while journeying the forty years in the wilderness; which, as before observed, seems to be the true reason of the omission of circumcision.