Joshua 5:3

I may wish in this place to inquire of the Jews how anyone is able to be circumcised a second time with the circumcision of the flesh. For once anyone is circumcised, he does not have anything more to be removed a second time. But see how fittingly and consistently those things may be resolved by us, to whom it is said, "The law is spiritual." For we say that that person who was skilled in the law and taught by Moses cast off the errors of idolatry and put aside the superstition and worship of images. This is the first circumcision through the law. But if he comes from the law and the prophets to the gospel faith, then he also receives the second circumcision through "the rock, who is Christ," and what the Lord said to Jesus [Joshua] is accomplished: "Today I have taken away the reproach of Egypt from the sons of Israel."Just as the apostle said, "They drank from the spiritual rock following them, but that rock was Christ," so also we are able to say aptly in this place that they were circumcised "from the spiritual rock following them, but the rock was Christ." For if anyone has not been cleansed through the gospel by a second circumcision, he is not able to put aside the reproach of Egypt, that is, the allurement of fleshly vices.

Also Moses himself: "In the last days the Lord God will circumcise your heart that you may love the Lord your God." And in like manner in Jesus [Joshua], the son of Nun, the successor of Moses, we note: "And the Lord said to Jesus [Joshua]: Make for yourself knives of stone exceedingly sharp and sit and circumcise a second time the children of Israel." He said that this second circumcision would not be of the flesh as was the first, which the Jews still practice, but of the heart and spirit, which Christ, who was the true Jesus, gave.

The former is said to have circumcised the people a second time with knives of stone (which was a sign of this circumcision with which Jesus Christ Himself has circumcised us from the idols made of stone and of other materials), and to have collected together those who were circumcised from the uncircumcision, i.e., from the error of the world, in every place by the knives of stone, to wit, the words of our Lord Jesus. For I have shown that Christ was proclaimed by the prophets in parables a Stone and a Rock. Accordingly the knives of stone we shall take to mean His words, by means of which so many who were in error have been circumcised from uncircumcision with the circumcision of the heart, with which God by Jesus commanded those from that time to be circumcised who derived their circumcision from Abraham, saying that Jesus (Joshua) would circumcise a second time with knives of stone those who entered into that holy land.

In the course of the appointing of a successor to Moses, Hoshea the son of Nun is certainly transferred from his pristine name and begins to be called Jesus [Joshua]. Certainly, you say. This we first assert to have been a figure of the future. For, because Jesus Christ was to introduce the second people (which is composed of us nations, lingering deserted in the world previously) into the land of promise, "flowing with milk and honey" (that is, into the possession of eternal life, than which nothing is sweeter).

Now, this was a figure of baptism, for, just as circumcision cuts off from the body a part which is not useful but a useless superfluity, so by holy baptism are we circumcised of sin. It is obvious that sin is a superfluity of concupiscence and of no use. For it is impossible for anyone not to have any concupiscence at all or to be entirely without any taste for pleasure, but the useless part of pleasure, this is the sin which holy baptism circumcises.