Irenaeus Against Heresies Book III Hereby know ye the Spirit of God: Every spirit that confesseth that Jesus Christ is come in the flesh is of God; and every spirit which separates Jesus Christ is not of God, but is of antichrist."[297] Tertullian Against Marcion Book V by the Apostle John, who says that "already many false prophets are gone out into the world," the fore-runners of Antichrist, who deny that Christ is come in the flesh,[740] Dubious Hippolytus Fragments Believe not every spirit, because many false prophets are gone out into the world."[37]