Charles Ellicott Commentary Numbers 18:25

"And Jehovah spake unto Moses, saying," — Numbers 18:25 (ASV)

And the Lord spake unto Moses... — The law respecting the Levitical dues was given to Aaron, and communicated through him to the people. The law respecting the tithe which the Levites were to give to the priests, in which Aaron’s family were directly concerned, was communicated to Moses, and by him to the Levites.