Numbers 18:20
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. 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.
Aaron was to have no landed inheritance and no share among Israel, because the Lord Himself was his portion and inheritance among the people. That same landlessness belonged also to the Levites as the ministers of the sanctuary. They thus formed the sole exception to the division of Canaan among the people.