Charles Ellicott Commentary Leviticus 11:1

"And Jehovah spake unto Moses and to Aaron, saying unto them," — Leviticus 11:1 (ASV)

And the Lord spake unto Moses and to Aaron. — So that the rebuke which Moses publicly administered to the priests would not diminish their influence with the people, whom they had to teach the laws of clean and unclean things laid down in the following chapters, the Lord here honors Aaron, as well as Moses, by making this communication to them jointly. Besides, Aaron as minister was as much concerned with these laws as Moses the legislator. Therefore, when a question of defilement later had to be decided, it was brought for judgment before Moses and Aaron jointly .