Numbers 35:4-5

And the suburbs of the cities, which ye shall give unto the Levites, shall be from the wall of the city and outward a thousand cubits round about.

And ye shall measure without the city for the east side two thousand cubits, and for the south side two thousand cubits, and for the west side two thousand cubits, and for the north side two thousand cubits, the city being in the midst. This shall be to them the suburbs of the cities.