Numbers 35:2-5

2Command the children of Israel, that they give to the Levites of the inheritance of their possession cities to dwell in; and ye shall give also to the Levites common lands for the cities around them.

3And they shall have the cities to dwell in; and the common lands of them shall be for their cattle, and for their goods, and for all their beasts.

4And the common lands of the cities, which ye shall give to the Levites, shall reach from the wall of the city and outward a thousand cubits on all sides.

5And ye shall measure from outside the city on the east side two thousand cubits, and on the south side two thousand cubits, and on the west side two thousand cubits, and on the north side two thousand cubits; and the city shall be in the midst: this shall be to them the common lands of the cities.