Against Celsus 5.48

Even if the Jews pride themselves on circumcision, they will distinguish it not only from the circumcision of the Colchians and Egyptians but also from that of the Ishmaelite Arabs, although Ishmael was born of their forefather Abraham and was circumcised with him. The Jews say that circumcision on the eighth day is the principal one, and that which is not so is from circumstance; and perhaps it was performed because of an angel hostile to the Jewish nation, who was able to harm those of them who were not circumcised but was powerless against those who were circumcised. Someone will say this is shown by what is written in Exodus, where the angel was able to act against Moses before the circumcision of Eliezer, but when he was circumcised had no strength. And having learned such things, "Zipporah took a stone and circumcised" her child; according to the common copies she is recorded to have said, "The blood of my child's circumcision is stanched," but according to the Hebrew itself, "You are a bridegroom of blood to me." For she knew the account of this angel, who had power before the blood and ceased because of the blood of circumcision; for which reason it was said to him: "You are a bridegroom of blood to me." But let these matters, which seem rather curious and not suited to the hearing of the many, be ventured thus far; I will add one thing to them, as befits a Christian, and pass on to what follows. This angel, I think, had power against those of the people who were not circumcised, and in general against all who worship the Creator alone, and had power as long as Jesus had not taken a body. But when he took one, and his body was circumcised, all this angel's power against those circumcised in this religion was destroyed; for Jesus destroyed him by his unspeakable divinity. That is why his disciples are forbidden to be circumcised, and it is said to them: "If you are circumcised, Christ will be of no benefit to you."