John Gill Commentary Joshua 5:7

"And their children, whom he raised up in their stead, them did Joshua circumcise: for they were uncircumcised, because they had not circumcised them by the way." — Joshua 5:7 (ASV)

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 whom might be near forty years of age; as for those that were born before, of whom 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.