Cyprian of Carthage, Three Books of Testimonies Against the Jews III.51: That the sacrament of faith must not be profaned

In Solomon, in the Proverbs: “Say not anything in the ears of a foolish man; lest, when he hears it, he may mock at thy wise words.” Also in the Gospel according to Matthew: “Give not that which is holy to dogs; neither cast ye your pearls before the swine, lest perchance they trample them down with their feet, and turn again and crush you.”