Moses
Leviticus 21:1ESV·traditional attribution

And the LORD said to Moses, “Speak to the priests, the sons of Aaron, and say to them, No one shall make himself unclean for the dead among his people,

John Calvin Reformed @genevareformer

1. Speak unto the priests. All these things which follow tend to the same end, i.e., that the priests may differ from the rest of the people by notable marks, as if separated from ordinary men; for special purity became those who represented the person of Christ.

Matthew Henry Presbyterian @wholebiblehenry

It was before appointed that the priests should teach the people the statutes God had given concerning the difference between clean and unclean, Lev 10:10, Lev 10:11. Now here it is provided that they should themselves observe what they were to teach the people. Note, Those whose office it is to instruct must do it by example as well as precept, Ti1 4:12.

Commenting on Leviticus 21:1-9

John Gill Reformed Baptist @doctorgill

And the Lord said unto Moses,.... According to some Jewish writers this was said on the day the tabernacle was set up; no doubt it was delivered at the same time the above laws were given; and as care was taken for the purity and holiness of the Israelites in general, it was necessary that the priests that were concerned in a more especial manner...