They; either their parents, or the rulers of Israel, whose omission hereof was not through neglect; for then God, who had ordered the neglecter of circumcision to be cut off, Genesis 17:14, would not have left so gross a fault unpunished; but by Divine permission and indulgence; partly because they were now in a journey, in which case the passover also might be neglected, Numbers 9:10,13, and in that journey the passover was but once observed; and partly because there was not so great a necessity of this note of circumcision to distinguish them from other nations, whilst they dwelt alone and unmixed in the wilderness, as there was afterwards.
Related Commentaries of Joshua 5:5
Joshua 5:5
5 Now 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, them they had not circumcised.