Lactantius

“ And not more mild than these are those offerings which are even now made to the Great Mother and to Bellona, in which the priests make an offering, not with the blood of others, but with their own blood; when, mutilating themselves, they cease to be men, and yet do not pass over to the women; or, cutting their shoulders, they sprinkle the loathsome altars with their own blood. But these things are cruel.
Let us come to those which are mild. The sacred rites of Isis show nothing else than the manner in which she lost and found her little son, who is called Osiris. ”