Why did the Levi'im not receive a portion in Eretz Yisrael?
Rashi: Because, since they are designated for the service of the Mizbe'ach, they are not free to plow and sow when necessary.
Ramban: Because they are all obligated to assist the Kohanim
in their service.
Because whatever was performed in the Beis ha'Mikdash was for the sake of the Korbanos.
What does the Torah mean when it writes "Hashem Hu Nachalaso"?
Rashi: They are financed
from 'the house of the King.
Targum Onkelos and Targum Yonasan: It means that the Matanos that Hashem gives them is their portion.
I.e. Ma'aser, and cities to live in (Hadar Zekenim, Rosh).