Deuteronomy 18:1

The priests of the tribe of Levi will have no part or inheritance with their brethren: they shall eat the oblations of the Lord as their portion,

the Levite priests Having mentioned the regulations pertaining to the sovereign, who is the Chief Justice, Scripture now mentions certain ordinances concerning the priests, who are the teachers of the Law. And, since they have no land allotted to them, they shall take from every sacrifice the shoulder, the cheeks, and the stomach. The shoulder — from the body; the cheeks (including the tongue) — from the head; and the stomach — from the internal organs. There is a homiletical explanation, based on the fact that the kohanim slaughter the peace-offerings [the halakha [Zevaḥim 31b] is that a non-kohen may slaughter the sacrifice — Translator], which depicts the shoulder as the reward for the slaughtering, which is done with one’s arm; the cheeks are the reward for the recitation of the benediction; and the stomach is the reward for the inspection of the internal organs. But the straightforward meaning is that these are the choicest cuts of meat. Scripture also mentions the matter of the Levite, because he is a teacher of the Torah as well, in the provinces. This is evident from Chronicles [II Chronicles 17: 7 ff].

THE FIRE OFFERINGS OF THE ETERNAL — “the hallowed offerings of the Sanctuary. AND HIS INHERITANCE — these are hallowed gifts that may be consumed outside of the Sanctuary and Jerusalem, such as the heave-offerings and the tithes. 2. BUT a real INHERITANCE SHALL HE [the tribe of Levi] NOT HAVE AMONG HIS BRETHREN. In the Sifre the Rabbis interpreted this verse: 164. See Vol. II, pp. 163-164 where Ramban refers to this subject briefly and makes a short reference to Rashi’s text before us. He will also refer to it further on. ‘But an inheritance shall he not have — this refers to the inheritance of the rest [of the nations]. Among his brethren — this refers to the inheritance of the seven.’ I do not know what this means. But it appears to me that the land of Canaan, which extends from the [western] side of the Jordan, is called the land of ‘the five nations;’ the land of Sihon and Og is called the land of two nations, the Amorites and the Canaanites; and ‘the inheritance of the rest’ includes the lands of the Kenites, Kenizzites, and Kadmonites [which are to be given to Israel in the future]. Then the following statement was found in the words of Rabbi Klonimus: Thus we must read in the Sifre, ‘But an inheritance shall he not have — this refers to the inheritance of the five nations. Among his brethren — this refers to the inheritance of the seven.’ And [Rabbi Klonimus explained the Sifre as meaning] the inheritance of the five tribes, and the inheritance of the seven tribes. Now, because Moses and Joshua assigned an inheritance only to five tribes — for Moses assigned an inheritance to Reuben, Gad and the half-tribe of Menasheh, and Joshua assigned an inheritance to Judah, Ephraim, and the other half of the tribe of Menasheh. The other seven took their own portions after the death of Joshua. Therefore [the Sifre] mentioned the five [tribes] separately and the seven [tribes] separately.” All this is Rashi’s language.
Now, I have already explained the main interpretation [of this Sifre] in the section Sanctify unto Me,, Verse 5 (Vol. II, pp. 163-164). that “the inheritance of the five” is mentioned in the verse, And it shall be when the Eternal shall bring thee into the land of the Canaanite, and the Hittite, and the Amorite, and the Hivite, and the Jebusite, which He swore unto thy fathers to give thee, a Land flowing with milk and honey, constitute a change, Verse 5. these comprising the main Land which He promised them, for that was the Land flowing with milk and honey. But the two remaining lands, those of the Perizzite and the Girgashite, were not flowing with milk and honey and are not obligated in the commandment of first-fruits. Therefore, he mentioned regarding the Levites that they are not to take a portion with Israel [either] in the main part of their inheritance in the good land which is “the inheritance of the five” [nations], and not even in the inheritance of “the seven” [nations] which contain the two remaining ones [the Perizzite and the Girgashite] — although their lands were not good and were not considered so worthy in the eyes of the Israelites. This is a clear interpretation [of this Sifre] on the basis of proofs I have written there., Verse 5 (Vol. II, pp. 163-164).