Adam Clarke, on Gen 17:12

“An infant of eight days old shall be circumcised among you, every man child in your generations: he that is born in the house, as well as the bought servant shall be circumcised, and whosoever is not of your stock:”

“He that is eight days old - Because previously to this they were considered unclean, Lev 12:2, Lev 12:3, and circumcision was ever understood as a consecration of the person to God. Neither calf, lamb, nor kid, was offered to God till it was eight days old for the same reason, Lev 22:27.”

Imported from an open dataset — not yet checked against the printed edition.