The priest shall - pronounce him unclean - וטמא אתו vetimme otho; literally, shall pollute him, i. e., in the Hebrew idiom, shall declare or pronounce him polluted; and in Leviticus 13:23, it is said, the priest shall pronounce him clean, וטהרו הכהן vetiharo haccohen, the priest shall cleanse him, i. e., declare him clean. In this phrase we have the proper meaning of Matthew 16:19 : Whatsoever ye bind on earth, shall be bound in heaven; and whatsoever ye loose on earth shall be loosed in heaven. By which our Lord intimates that the disciples, from having the keys, i. e., the true knowledge of the doctrine, of the kingdom of heaven, should, from particular evidences, be at all times able to distinguish between the clean and the unclean, the sincere and the hypocrite; and pronounce a judgment as infallible as the priest did in the case of the leprosy, from the tokens already specified. And as this binding and loosing, or pronouncing fit or unfit for fellowship with the members of Christ, must in the case of the disciples be always according to the doctrine of the kingdom of heaven, the sentence should be considered as proceeding immediately from thence, and consequently as Divinely ratified. The priest polluted or cleansed, i. e., declared the man clean or unclean, according to signs well known and infallible. The disciples or ministers of Christ bind or loose, declare to be fit or unfit for Church fellowship, according to unequivocal evidences of innocence or guilt. In the former case, the priest declared the person fit or unfit for civil society; in the latter, the ministers of Christ declare the person against whom the suspicion of guilt is laid, fit or unfit for continued association with the Church of God. The office was the same in both, a declaration of the truth, not from any power that they possessed of cleansing or polluting, of binding or of loosing, but by the knowledge they gained from the infallible signs and evidences produced on the respective cases.

Leviticus 13:8 "The priest shall look, and if the scab has spread on the skin, then the priest shall pronounce him unclean; it is leprosy.

Leviticus 13:10 "The priest shall then look, and if there is a white swelling in the skin, and it has turned the hair white, and there is quick raw flesh in the swelling,

The Third Commandment
Thou shalt not take the name of the Lord thy God in vain: For the Lord will not hold him guiltless that taketh his name in vain.' Exod 20: 7. This commandment has two parts: 1. A negative expressed, that we must not take God's name in vain; that is, cast any reflections and dishonour on his name. 2. An affirmative implied. That we should take care to reverence and honour his name. Of this latter I shall speak more fully, under the first petition in the Lord's Prayer, Hallowed be thy name.' I shall …
Thomas Watson—The Ten Commandments