And the Lord spake unto Aaron, Thou shalt have no inheritance in their land, neither shalt thou have any part among them: I am thy part and thine inheritance among the children of Israel. (Numbers 18:20)
That is, the Levites received no territorial inheritance in the Holy Land as did the other tribes. Aaron himself did not enter into the Holy Land, but this statement is made to him as the representative of the Levites. Certain sacred dues were to take the place of a landed inheritance.
I am thy part.
The priests were devoted altogether to God (Deut. 10:9). On their part, the people were to manifest a spirit of generosity toward their brethren the priests, who had not been provided with a landed inheritance (see Deut. 12:12; Joshua 13:14). The priests lived from God’s altar and were fed, as it were, at God’s table.