Luke 17:11

After speaking the foregoing parable, our Lord censures the ungrateful...

(de Quæst. Ev. l. ii. qu. 40.) The lepers may be taken mystically for those who, having no knowledge of the true faith, profess various erroneous doctrines. For they do not conceal their ignorance, but blazen it forth as the highest wisdom, making a vain show of it with boasting words. But since leprosy is a blemish in colour, when true things appear clumsily mixed up with false in a single discourse or narration, as in the colour of a single body, they represent a leprosy streaking and disfiguring as it were with true and false dyes the colour of the human form. Now these lepers must be so put away from the Church, that being as far removed as possible, they may with loud shouts call upon Christ. But by their calling Him Teacher, I think it is plainly implied that leprosy is truly the false doctrine which the good teacher may wash away. Now we find that of those upon whom our Lord bestowed bodily mercies, not one did He send to the priests, save the lepers, for the Jewish priesthood was a figure of that priesthood which is in the Church. All vices our Lord corrects and heals by His own power working inwardly in the conscience, but the teaching of infusion by means of the Sacrament, or of catechizing by word of mouth, was assigned to the Church. And as they went, they were cleansed; just as the Gentiles to whom Peter came, having not yet received the sacrament of Baptism, whereby we come spiritually to the priests, are declared cleansed by the infusion of the Holy Spirit. Whoever then follows true and sound doctrine in the fellowship of the Church, proclaiming himself to be free from the confusion of lies, as it were a leprosy, yet still ungrateful to his Cleanser does not prostrate himself with pious humility of thanksgiving, is like to those of whom the Apostle says, that when they knew God, they glorified him not as God, nor were thankful. (Rom. […]

Marcion's labour, however, is to object to us the strictness of the law, with the view of maintaining that here also Christ is its enemy-forestalling its enactments even in His cure of the ten lepers. These He simply commanded to show themselves to the priest; "and as they went, He cleansed them" -without a touch, and without a word, by His silent power and simple will.

Again the Saviour manifests unto us His glory, and by working godlike miracles, endeavours to win senseless Israel unto faith, obdurate though he was, and unbelieving. What argument then will avail him at the day of judgment for refusing to accept salvation through Christ? Especially when they themselves heard His words, and were eyewitnesses of His ineffable miracles? The cleansing of the lepers, as I said just above, was a plain demonstration (of His miraculous power): for by the law of Moses they were shut out of the cities and villages, as being impure. The lepers then having met the Saviour, earnestly besought Him to free them from their misery, and called Him Master, that is, Teacher. No one pitied them when suffering this malady: but He Who had appeared on earth for this very reason, and had become man that He might show pity unto all, He was moved with compassion for them, and had mercy upon them. And why did He not rather say, "I will, be you cleansed;" as he did in the case of another leper: but commanded them rather to show themselves unto the priests? It was because the law gave directions to this effect to those who were delivered from leprosy: for it commanded them to show themselves to the priests, and to offer a sacrifice for their cleansing. He commanded them therefore to go, as being already healed, and, that they might, so to speak, bear witness to the priests, as the rulers of the Jews, and ever envious of His glory, that wonderfully, and beyond their hope, they had been delivered from their misfortune by Christ's willing that they should be healed.

saying, And it came to pass, showing that the Samaritans were indeed well disposed towards the mercies above mentioned, but the Jews not so. For there was enmity between the Jews and the Samaritans, and He to allay this, passed into the midst of both nations, that he might cement both into one new man.