In 35:6-8, after Hashem and Moshe just appointed Yehoshua and some Nesiim to be the executors of the division of Eretz Yisrael, the Torah talks about the cities of refuge. It says the Levite tribe would not receive a portion but would be allotted the 6 cities of refuge, along with an additional 42 cities spread out among Israel.
Why did they not get a portion like every other tribe? If any one tribe was deserving of being given a portion, it would be them! They were completely dedicated to the service of Hashem. They were the ones who never strayed from doing the right thing (aside from korach, but that was individuals). So why were they not given a portion, but spread out in specific cities taken form the portions of other tribes?
Maybe the reason is because the Leviim were so dedicated to the service of Hashem. Much more so that any other group or tribe.
If Hashem gave them a portion, they would be fairly isolated. they would continue living a life dedicated to Hashem and all would be very nice.
But by mixing them among all the other tribes, life can be even better. By not being isolated in their own portion, but by living among the other tribes, they can show the rest of the Nation how to live a life of dedication. They can teach the people. They can influence.
When one has what to offer, he should not remain isolated. he should share it with everyone else.