And in the eighth day the flesh of his foreskin shall be circumcised. Or the foreskin of his flesh, that is, of the man child born according to the law, Ge 17:12 and this seems to furnish out a reason why a male child was not circumcised before the eighth day, and why it was then, because before that its mother was in her separation and uncleanness, and then was freed from it; and so the Targum of Jonathan.
The circumcision of a male child on the eighth day was religiously observed, and even was not omitted on account of the sabbath, when the eighth day happened to be on that,See Gill on "Joh 7:22" see Gill on "Joh 7:23".