"The fire-offerings of the L-rd and His inheritance shall they eat": "the fire offerings": the Temple offerings. Whence do I derive the same for the boundary offerings (i.e., the terumoth and ma'aseroth of Eretz Yisrael)? From "and His inheritance shall they eat."
(Devarim 18:2) "And an inheritance he shall not have in the midst of his brothers": This is the inheritance of the three (peoples — Keini, Kenizi, Kadmoni).