Rashi on Deuteronomy 12:18/רש"י על דברים י״ב:י״ח

1לפני ה׳ [BUT THOU MUST EAT THEM] BEFORE THE LORD — i.e. within the walls of the city of Jerusalem.

2והלוי אשר בשעריך [BUT THOU MUST EAT THEM BEFORE THE LORD, THOU …] AND THE LEVITE THAT IS WITHIN THY GATES — If you have nought to give him that is due to him as his portion, as, for instance, the first tithe, give him the “tithe of the poor” (the tithe that replaces the “second tithe” in the 3rd and 6th year of the Sabbatical period); and if you have no “tithe of the poor”, invite him to your feast-offering meal (Sifrei Devarim 74:5).