Origen — on 2Cor 3:6 (HOMILIES ON LEVITICUS 7.5.5)

“For even in the Gospels, it is "the letter" that "kills." Not only in the Old Testament is "the letter that kills" found; there is also in the New Testament "the letter that kills"—that one who does not spiritually perceive what is said. For, if you follow according to the letter that which is said, "Unless you eat my flesh and drink my blood," this "letter kills." Do you want me to bring out of the gospel for you another "letter" that "kills"? He says, "Let the one who does not have a sword sell his tunic and buy a sword." Behold, this is the letter of the gospel, but "it kills." But, if you take it spiritually, it does not kill, but there is in it "a spirit that gives life." For this reason, receive spiritually what is said either in the law or in the Gospels because "the spiritual one judges all things but that one is not judged by anyone."”