Augustine of Hippo, On the Spirit and the Letter Chapter 23: How the Decalogue Kills, If Grace Be Not Present

Although, therefore, the apostle seems to reprove and correct those who were being persuaded to be circumcised, in such terms as to designate by the word “law” circumcision itself and other similar legal observances, which are now rejected as shadows of a future substance by Christians who yet hold what those shadows figuratively promised; he at the same time nevertheless would have it to be clearly understood that the law, by which he says no man is justified, lies not merely in those sacramental institutions which contained promissory figures, but also in those works by which whosoever has done them lives holily, and amongst which occurs this prohibition: “Thou shalt not covet.” Now, to make our statement all the clearer, let us look at the Decalogue itself. It is certain, then, that Moses on the mount received the law, that he might deliver it to the people, written on tables of stone by the finger of God. It is summed up in these ten commandments, in which there is no precept about circumcision, nor anything concerning those animal sacrifices which have ceased to be offered by Christians. Well, now, I should like to be told what there is in these ten commandments, except the observance of the Sabbath, which ought not to be kept by a Christian,—whether it prohibit the making and worshipping of idols and of any other gods than the one true God, or the taking of God’s name in vain; or prescribe honour to parents; or give warning against fornication, murder, theft, false witness, adultery, or coveting other men’s property? Which of these commandments would any one say that the Christian ought not to keep? Is it possible to contend that it is not the law which was written on those two tables that the apostle describes as “the letter that killeth,” but the law of circumcision and the other sacred rites which are now abolished? But then how can we think so, when in the law occurs this precept, “Thou shall not covet,” by which very commandment, notwithstanding its being holy, just, and good, “sin,” says the apostle, “deceived me, and by it slew me?” What else can this be than “the letter” that “killeth”?