Rom 16:19

“The ancient race was perverse and hard-hearted; but the band of infants, the new people which we are, is delicate as a child. On account of the hearts of the innocent, the apostle, in the Epistle to the Romans, owns that he rejoices, and furnishes a kind of definition of children, so to speak, when he says, "I would have you wise toward good, but simple towards evil."”

“On account of the hearts of the innocent, the apostle, in the Epistle to the Romans, owns that he rejoices, and furnishes a kind of definition of children, so to speak, when he says, "I would have you wise toward good, but simple towards evil." ...But if, which is rather the true sense, they themselves understand the designation children of simple ones, we glory in the name. For the new minds, which have newly become wise, which have sprung into being according to the new covenant, are infantile in the old folly.”

“"For your obedience is come abroad unto all men." This he does, not to leave them free to be shameless, but to win them beforehand with encomiums, and the number of his witnesses, to arrest their attention. For neither is it I alone that am the witness, but the whole world. And he does not say for your understanding, but, "your obedience:" that is, their compliance, which was evidence of much meekness in them. "I am glad therefore on your behalf." And this is no small encomium too. Then, after the praise, admonition. For lest, after liberating them from any charges against them, he should make them the more listless, as not being observed; he gives them another hint in the words, "I would have you wise unto that which is good, and simple concerning evil." You see then how he attacks them again, and that without their suspecting it. For this looks like intimating that some of them were apt to be led astray.”

“If you obeyed those you should not have obeyed, how much more should you obey us! For this is why these people came to you, because they knew that you could readily be led astray by unsuspecting obedience. I rejoice with you, because obedience is good only if it is reasonable. I want you to be wise in what is good, so that by being ignorant of evil you may bring the enemy down under the feet of innocence.”

“They deceive, he said, the simple-hearted. But "your obedience," which comes from great meekness, is known to all: I alone do not bear witness to it, but the whole world. Therefore I rejoice for you, that you were not deceived. He hints at the fact that some of them also had been led astray. He clearly expresses the same thing that the Lord said: "be wise as serpents, and harmless as doves" (Matt. 10:16). For he desires that they be "wise" or cautious "unto good," that is, in the matter of their own salvation and their own benefit, and "simple concerning evil," that is, in not doing harm to others, for the simple person causes no one harm.”

“He assigns the second reason from a trait of the Romans, who found it easy to follow good and evil. First, he commends them for their readiness to accept the good, saying: for your obedience, by which you obey the faith so easily, is published in every place on account of the dominion the Romans then exercised over other nations. Hence, anything done by the Romans was easily divulged to others. Your faith is proclaimed in the whole world (Rom 1:8). I rejoice, therefore, in you, because you obey the faith; and this in charity, about which he says that love does not rejoice at wrong, but rejoices in the truth (1 Cor 13:6). Second, he cautions them against evil, saying: but I would have you to be wise in good, so that you might cling to what is good, and simple in evil, lest through some simplicity you decline to evil, so that your simplicity be such that you deceive no one into evil: be wise as serpents and simple as doves (Matt 10:16). On the other hand, it is said of certain persons: they are skilled in doing evil, but how to do good they know not (Jer 4:22).”