Tertullian, On Monogamy 1

Heretics abolish marriage; Psychics multiply it. The former refuse to marry even once, the latter refuse to stop at once. What are you doing, law of the Creator? You complain about domestic obedience just as much as foreign contempt, so both those who abuse marriage and those who refuse it wound you alike. Truly, such continence deserves no praise because it is heretical, and such license deserves no defense because it is psychic. The one blasphemes; the other wallows in lust. The one destroys the God of marriage; the other confuses him. But among us—who are rightly called spiritual because we acknowledge spiritual gifts—continence is as devout as license is modest, since both stand with the Creator. Continence honors the law of marriage; license moderates it. The former is not forced; the latter is governed. The former exercises judgment; the latter observes measure. We know one marriage, just as we know one God. The law of marriage gains greater honor where it also has shame. Yet Psychics, because they do not receive the Spirit, find no pleasure in the things of the Spirit. So while the things of the Spirit displease them, the things of the flesh will please them, as contrary to the Spirit. "The flesh," it says, "desires against the Spirit, and the Spirit against the flesh" (Gal 5:17). What, then, will the flesh desire except what is more fleshly? Because of this, the flesh was also made alien to the Spirit from the beginning: "My Spirit," it says, "will not remain in these men forever, because they are flesh" (Gen 6:3).