Under the law, priest could only declare a person clean or unclean. He had no power to heal. Further, under the law touching someone or something that was unclean made you unclean as well.

But alleluia we are now under grace! As priests, each of us are now part of a holy priesthood, our job is not to declare the cleanness or un-cleanness of a person. Our job is to stretch forth our hands and heal. Under grace, we don’t have to worry about becoming unclean. The power of grace is that it makes the unclean, clean.

Remember, you are under grace and no longer under the law. You have been declared clean. You have been made whole. And now as a priest, you can heal those who are hurting, those who society has declared unclean, those who have been isolated. That is the power of grace!

“The priest will examine the affected area of the skin. If the hair in the affected area has turned white and the problem appears to be more than skin-deep, it is a serious skin disease, and the priest who examines it must pronounce the person ceremonially unclean.”
‭‭Leviticus‬ ‭13:3‬ ‭NLT‬‬
http://bible.com/116/lev.13.3.nlt