Romans 16:19

19.Your obedience, (481) etc. This is said to anticipate an objection; for he shows that he did not warn them, as though he thought unfavorably of them, but because a fall in their case was such as might have easily happened; as if he had said, — “Your obedience is indeed commended everywhere, and for this reason I rejoice on your account: yet since it often happens, that a fall occurs through simplicity, I would have you to be harmless and simple as to the doing of evil; but in doing good, to be most prudent, whenever it may be necessary, so that you may preserve your integrity.”

We here see what that simplicity is which is commended in Christians; so that they have no reason to claim this distinction, who at this day count as a high virtue their stupid ignorance of the word of God. For though he approves in the Romans, that they were obedient and teachable, yet he would have them to exercise wisdom and judgment, lest their readiness to believe exposed them to impositions. So then he congratulates them, because they were free from a wicked disposition; he yet wished them to be wise, so as to exercise caution. (482)