Charles Ellicott Commentary Leviticus 24:9

"And it shall be for Aaron and his sons; and they shall eat it in a holy place: for it is most holy unto him of the offerings of Jehovah made by fire by a perpetual statute." — Leviticus 24:9 (ASV)

And it shall be Aaron’s and his sons’. —In accordance with this statute, the twelve cakes were divided during the second Temple between the high priest and the officiating priests; the former had six, and the latter had six among them.

They shall eat it in the holy place. —Of the many things connected with the national service that became the portions of the priests, there were only eight that had to be consumed within the precincts of the sanctuary, and the shewbread is one of the eight, namely:

1. The remnant of the meat offering (Leviticus 2:3; Leviticus 2:10);
2. The flesh of the sin offering (Leviticus 6:26);
3. The flesh of the trespass offering (Leviticus 7:6);
4. The leper’s log of oil (Leviticus 14:10);
5. The remainder of the omer (Leviticus 23:10–11);
6. The peace offering of the congregation;
7. The two loaves (Leviticus 13:19–20); and
8. The shewbread.

Of the offerings of the Lord made by fire. —That is, the former part of the offering—specifically, the frankincense, which was the other component—was burned as an offering to God.