Likewise, i.e. ye shall offer their first-born. On the eighth day; not sooner, because it was till then tender and imperfect, and therefore not fit to be offered to God; but it was not tied to that day, for it might be offered afterwards, appears from Leviticus 22:27, even till it was a year old.
Related Commentaries of Exodus 22:30
Exodus 22:30
30 Likewise shalt thou do with thine oxen, and with thy sheep: seven days it shall be with his dam; on the eighth day thou shalt give it me.