Genesis 17:27

And all the men of his house
All the males, whether children or adult:

born in the house, or bought with money of the stranger, were
circumcised with him;
by their will, and with their consent; not forced to it, as Aben Ezra rightly observes; and these being before trained up by him in religious exercises, were more easily prevailed upon by him to follow his example; this also is repeated, that it might be served, and be an example to follow in after generations.