Charles Ellicott Commentary Leviticus 17:2

"Speak unto Aaron, and unto his sons, and unto all the children of Israel, and say unto them: This is the thing which Jehovah hath commanded, saying," — Leviticus 17:2 (ASV)

And unto all the children of Israel. —To understand the significance of this phrase, and its relevance to the command in question, it is necessary to note that the words “and unto all the children of Israel” are used here for the first time.

Until now, the Divine communications were made:

1. to Moses alone, without his being ordered to speak to anyone else (Leviticus 5:14; Leviticus 6:12; Leviticus 8:1; Leviticus 14:1);
2. to Moses, with the command to speak to Aaron (Leviticus 16:1);
3. to Moses, with the command to speak to Aaron and his sons (Leviticus 6:1; Leviticus 6:17);
4. to Moses, with a command to speak to the children of Israel (Leviticus 1:1; Leviticus 4:1; Leviticus 7:28; Leviticus 12:1);
5. to Moses and Aaron conjointly, without being ordered to speak to the children of Israel (Leviticus 13:1; Leviticus 14:33);
6. to Moses and Aaron conjointly, who are ordered to speak to the children of Israel (Leviticus 11:1; Leviticus 15:1); and
7. when Aaron alone was addressed (Leviticus 10:8).

In this chapter, however, the communication is made to Moses alone, and he is commanded not only to impart its contents to Aaron and his sons—that is, the priesthood—but “unto all the children of Israel,” or their representatives, at the same time. The high priest and the priests are thus put on a level with the ordinary Israelite or the laity, as far as this regulation is concerned. There are only two other occasions on which this phrase is used again, namely, Leviticus 21:24; Leviticus 22:18.

This is the thing which the Lord hath commanded. —To emphasize the importance of the following law, Moses is ordered by God to use this additional formula; while in other instances where it is used, when important statutes are enacted, Moses uses it of his own accord (Exodus 35:4; Leviticus 8:5; Leviticus 9:6; Numbers 30:2; Numbers 36:6).