Exodus 29:33 "And they shall eat those things [the sacrifices] with which atonement was made"

When a sin offering or guilt offering is brought, it is a Mitzvah for the priest to eat from those portions that were not offered on the altar.

The eating of the meat is part of the atonement for the person who brings the sacrifice.

Deuteronomy 12:17 "You may not eat within your gates...the first- born of your herds or flocks"

Sometimes, portions of the sacrifices are eaten by the priests and others, by the person who brings them.

he sin-offerings and guilt-offerings must be eaten in the specific area of the Beit HaMikdash called the "Azarah", the Temple courtyard.

We are cautioned not to eat this sacrificial meat anywhere outside this area. (This Negative Mitzvah applies to priests as well.)

Deuteronomy 12:17 "You may not eat within your gates...the offering of your hand"

The first-fruits of the crop (Bikurim) must be brought to Jerusalem and given to the priest (See Positive Mitzvah 125).

This Negative Mitzvah prohibits the priest from eating these first-fruits outside of Jerusalem.