Numbers 35:8

5 The measure of this space of land is to be two thousand cubits outside the town on the east, and two thousand cubits on the south and on the west and on the north, the town being in the middle. This space will be the outskirts of their towns.

6 And the towns which you give the Levites are to be the six safe places to which the taker of life may go in flight; and in addition you are to give them forty-two towns.

7 Forty-eight towns are to be given to the Levites, all with land round them.

8 And these towns are to be given out of the heritage of the children of Israel, taking the greater number from those who have much, and a smaller number from those who have little: everyone, in the measure of his heritage, is to give of his property to the Levites.

9 And the Lord said to Moses,

10 Say to the children of Israel, when you have gone over Jordan into the land of Canaan;

11 Then let certain towns be marked out as safe places to which anyone who takes the life of another in error may go in flight.