Deuteronomy 24:8 in the King James Version
Take heed in the plague of leprosy, that thou observe diligently, and do according to all that the priests the Levites shall teach you: as I commanded them, so ye shall observe to do.
Context
7 If a man is found stealing any of his brothers of the children of Israel, and he deals with him as a slave, or sells him, then that thief shall die. So you shall remove the evil from among you.
8 Be careful in the plague of leprosy, that you observe diligently and do according to all that the Levitical priests teach you. As I commanded them, so you shall observe to do.
9 Remember what the LORD your God did to Miriam, by the way as you came out of Egypt.