7 Let the Marcionists also be abhorred, who tear away from the New Testament the sayings of the Old. For Marcion first, that most impious of men, who first asserted three Gods, knowing that in the New Testament are contained testimonies of the Prophets concerning Christ, cut out the testimonies taken from the Old Testament, that the King might be left without witness. Abhor those above-mentioned Gnostics, men of knowledge by name, but fraught with ignorance; who have dared to say such things of the Holy Ghost as I dare not repeat.
Source: Catechetical Lectures (New Advent)