משנה אויף במדבר 35:4

They give a karpaf [as an extension] for every town, the words of Rabbi Meir. But the sages say: they said [the of a] karpaf only in regard to two towns that if there was to this one [a piece] of land of seventy cubits and a fraction and to the other one [a piece of land] seventy cubits and a fraction, they can consider the karpaf as combining the two into one.

On that day Rabbi Akiva expounded, “You shall measure off two thousand cubits outside the town on the east side” (Numbers 35:5). But another verse states, “from the wall of the city outward a thousand cubits around” (vs. It is impossible to say that it was a thousand cubits since it has been already stated two thousand cubits; and it is impossible to say that it was two thousand cubits since it has been already stated a thousand cubits! How then is this so? A thousand cubits for the field [surrounding the city] and two thousand cubits for the Sabbath-limits. Rabbi Eliezer the son of Rabbi Yose the Galilean says: a thousand cubits for the field [surrounding the city] and two thousand cubits for fields and vineyards.

If an Israelite inherited from his mother's father who was a Levite, he cannot redeem it according to the order prescribed here. Also if a Levite inherited from his mother's father who was an Israelite, he cannot redeem it according to the order prescribed here, As it says, “As for the houses of the cities of the Levites” (Leviticus 25:32) [this order does not apply] unless he is a Levite and in the cities of the Levites, the words of Rabbi. The sages say: these things apply to the cities of the Levites. One may not turn a field into pasture land, nor pasture land into a field, nor pasture land into a city, nor a city into pasture land. Rabbi Eliezer said: When is this so? When it comes to the cities of the Levites, but when it comes to cities of Israelites one may turn a field into pasture land, pasture land into a field, pasture land into a city, but not a city into pasture land, in order that they should not destroy the cities of Israel. Priests and Levites may sell [a house] at any time and redeem it at any time, as it is said: “The Levites shall forever have the right of redemption” (Leviticus 25:32).