Mitzvah 445 – 446) Not to eat an unblemished firstborn animal outside of Jerusalem, and not to eat the flesh of an offering outside of its assigned place
“You may not eat in your gates…… and the firstborn of your cattle and your sheep” (Devarim 12,17)
It is a negative commandment that the Priest may not eat an unblemished firstborn outside Jerusalem, and likewise any person who is not a priest may not eat of a firstborn in any place for the commandment is that the priests who serve G-d should eat it. Concerning all of this it says “You may not eat in your gates…… and the firstborn of your cattle and your sheep”. A priest who transgresses this commandment and eats an olive sized quantity of an unblemished first born animal outside Jerusalem, or an Israelite who is not a priest who eats it in any place, is penalized.
It is a negative commandment not to eat the flesh of a sin offering or a guilt offering outside the walls of the courtyard and this applies even to the priests. Chazal have accepted that this prohibition is included when it says “You may not eat in your gates…… and the firstborn of your cattle and your sheep”. Likewise, one who eats animals that have been sanctified as kodshim kalim (the lesser form of sancity which includes peace offerings etc.) outside the wall (of Jerusalem) is included in this prohibition, for anyone who eats an item outside its designated place is referred to when it says “You may not eat in your gates”.
Amongst the roots of this commandment: to eat every offering in its designated place so that those who eat it will concentrate their hearts on the atonement which they attain by eating it as Chazal say “The priests eat and the owners receive atonement”. If they eat it in a different place, their concentration may wander from the matter at hand.
This prohibition applies in every place and at every time, even one who nowadays sanctifies a sin offering or a guilt offering, and then one transgresses and eats an olive sized quantity from it, even if he is a priest, is penalized.