"You shall not cook a goat in its mother's milk": It is only meat and milk that you are forbidden to cook together and not other forbidden things. For it would follow (otherwise), viz.: If it is forbidden to cook together meat and milk, each of which, in itself, is permitted, how much more so the other forbidden things in the Torah, each of which, in itself, is forbidden! It is, therefore, written (to indicate otherwise) "You shall not cook a kid in its mother's milk" (—that, specifically).