From these remarks it is evident, that when Jesus said “coarsely,” as Celsus terms it, “To him who shall strike you on the one cheek, turn the other also; and if any man be minded to sue you at the law, and take away your coat, let him have your cloak also,” He expressed Himself in such a way as to make the precept have more practical effect than the words of Plato in the Crito; for the latter is so far from being intelligible to ordinary persons, that even those have a difficulty in understanding him, who have been brought up in the schools of learning, and have been initiated into the famous philosophy of Greece. It may also be observed, that the precept enjoining patience under injuries is in no way corrupted or degraded by the plain and simple language which our Lord employs, but that in this, as in other cases, it is a mere calumny against our religion which he utters when he says: “But let this suffice as one example of the way in which this and other truths have been borrowed and corrupted. Any one who wishes can easily by searching find more of them.”
Source: Against Celsus (New Advent)