Whence is (the same derived for cooking) the milk of goats with sheep? It follows a fortiori, viz.: If in reviah (mating of animals) where the Torah permitted "fruit" with mother (in cooking) it forbade "fruit" with (milk of) mother, then here where in reviah it forbade "fruit with fruit" (i.e., mating goat and sheep), how much more so does it forbid (in cooking) "fruit" with (milk of) mother!