To teach when it is unclean, and when it is clean: this is the law of leprosy.

Wesley's Notes

14:57 To teach - To direct the priest when to pronounce a person or house clean or unclean. So it was not left to the priests power or will, but they were tied to plain rules, such as the people might discern no less than the priest.

King James Translators' Notes

when it is unclean...: Heb. in the day of the unclean, and in the day of the clean

Matthew Henry's Concise Commentary

14:54-57 When that God who is rich in mercy, for his great love wherewith he loved us, even when we were dead in sins, hath quickened us by his grace, Eph 2:4,5, we shall manifest the change by repenting, and forsaking former sins. Let us follow after holiness, and let us compassionate other poor lepers, and desire, seek, and pray for their cleansing.

Matthew Henry's Whole Bible Commentary

Verses 54-57

This is the conclusion of this law concerning the leprosy. There is no repetition of it in Deuteronomy, only a general memorandum given (Deu. 24:8), Take heed in the plague of leprosy. We may see in this law, 1. The gracious care God took of his people Israel, for to them only this law pertained, and not to the Gentiles. When Naaman the Syrian was cured of his leprosy he was not bidden to show himself to the priest, though he was cured in Jordan, as the Jews that were cured by our Saviour were. Thus those who are entrusted with the key of discipline in the church judge those only that are within; but those that are without God judgeth, 1 Co. 5:12, 13. 2. The religious care we ought to take of ourselves, to keep our minds from the dominion of all sinful affections and dispositions, which are both their disease and their defilement, that we may be fit for the service of God. We ought also to avoid all bad company, and, as much as may be, to avoid coming within the danger of being infected by it. Touch not the unclean thing, saith the Lord, and I will receive you, 2 Co. 6:17.