Matthew 8:4

For a testimony to them. That is, when the priest finds thee truly cured, make that offering which is ordained in the law. (Witham) --- He did this to give us an example of humility, and that the priests, by approving of his miracle, and being made witnesses to it, might be inexcusable, if they can still call him a transgressor of the law, and prevaricator. He moreover gives this public testimony to them of his divine origin. (St. John Chrysostom, hom. xxvi.) St. John Chrysostom, in his third book on the priesthood, says: "the priests of the old law had authority and privilege only to discern who were healed of leprosy, and to denounce the same to the people; but the priests of the new law have power to purify, in very deed, the filth of the soul. Therefore, whoever despiseth them, is more worthy to be punished than the rebel Dathan and his accomplices." Our Saviour willeth him to go and offer his gift or sacrifice, according as Moses prescribed in that case, because the other sacrifice, being the holiest of all holies, viz. his body, was not yet begun. (St. Augustine, lib. ii. & Evang. ii. 3. & cont. adver. leg. & Proph. lib. i. chap. 19, 20.)