25 In fulfillment of our promise that we would prove the reference to Christ in those passages selected by Faustus from the writings of Moses for adverse criticism, since we cannot here point out the reference to Christ which we believe to exist in all the writings of Moses, it becomes our duty to show that this commandment of Moses, that every prophet or prince should be killed who tried to turn away the people from their God, or to break any commandment, refers to the preservation of the faith which is taught in the Church of Christ.
Moses no doubt knew in the spirit of prophecy, and from what he himself heard from God, that many heretics would arise to teach errors of all kinds against the doctrine of Christ, and to preach another Christ than the true Christ. For the true Christ is He that was foretold in the prophecies uttered by Moses himself, and by the other holy men of that nation. Moses accordingly commanded that whoever tried to teach another Christ should be put to death. In obedience to this command, the voice of the Catholic Church, as with the spiritual two-edged sword of both Testaments, puts to death all who try to turn us away from our God, or to break any of the commandments.
And chief among these is Manichæus himself; for the truth of the law and the prophets convinces him of error as trying to turn us away from our God, the God of Abraham, and Isaac, and Jacob, whom Christ acknowledges, and as trying to break the commandments of the law, which, even when they are only figurative, we regard as prophetic of Christ.
Source: Reply to Faustus the Manichaean (New Advent)