Charles Ellicott Commentary Leviticus 10:18

"Behold, the blood of it was not brought into the sanctuary within: ye should certainly have eaten it in the sanctuary, as I commanded." — Leviticus 10:18 (ASV)

Behold, the blood of it. —According to the sacrificial law, the flesh of the sin offerings (the blood of which was not carried into the sanctuary) had to be eaten by the priests alone, in a holy place, as a part of the expiatory rites. (Leviticus 10:17.) It was the flesh of those sin offerings, the blood of which was carried into the sanctuary, which had to be burned. (Leviticus 4:16; Leviticus 6:23; Leviticus 6:30.) Now the blood of the people’s sin offering which was offered on this occasion was not carried into the sanctuary. (See Leviticus 9:9.)

Ye should indeed have eaten it. —Hence its flesh should have been eaten by Aaron and his two sons in the courtyard of the sanctuary, as Moses commanded in Leviticus 6:26.