Leviticus 25:33

And if a man purchase of the Levites
An house or city, as Jarchi, and which the following clause confirms, that is, if a common Israelite made such a purchase, then it was redeemable, but if a Levite purchased of a Levite, then, as the same writer observes, it was absolutely irredeemable: then the house that was sold, and the city of his possession, shall go
out in [the year of] jubilee;
to the original owner of it, as fields and houses in villages sold by the Israelites for the houses of the cities of the Levites [are] their possession
among the children of Israel;
and their only possession, and therefore if those, when sold, were irredeemable, they would entirely be without any; and hence care is taken they should not; so Jarchi observes, that the Levites had no possession of fields and vineyards, only cities to dwell in, and their suburbs; wherefore cities were to them instead of fields, and their redemption was as that of fields, that so their inheritance might not be broken off from them.