The people of the tribe of Levi were the ministers of God among the nation. Some in Aaron's family were priests who ministered in the temple. Others were singers, water carriers, but in one way or another, they were the ministers of God. So, when the distribution of the land came, they gave no land to the Levites. Instead, they received a tithe from all the other nations, from their brothers. The tithe of their brothers was for the tribe to maintain itself. And at the same time, they would receive land and cities from their brothers. This was God's way of saying that he didn't want his ministers to be isolated from the people, that he wanted his ministers to be among the people. It's interesting to see that God graciously placed his ministers among the people. But then, in Numbers 3:12, 13 there is a very interesting text. God says that he had consecrated all the firstborn sons of the animals and people to himself once they were free from slavery in Egypt… Then God raised the Levites as substitutes for all the firstborn in the rest of the tribes, and he says in this text, "[They] shall be mine, for all the firstborn are mine." This was a special way of being dedicated to God. It was a special way to serve him and to serve among their brothers.