Matthew Poole and continuators on Deuteronomy 18:6

6 And if a Levite come from any of thy gates out of all Israel, where he sojourned, and come with all the desire of his mind unto the place which the LORD shall chuse ;

Either for any private occasions, or to sojourn there for a season, or rather with full purpose to fix his abode, and to spend his whole time and strength in the service of God, as appears by the sale of his patrimony mentioned, v. 8. It seems probable that the several Priests were to come from their Cities to the Temple by turns, before Davids time, and it is certain they did so after it. But if any of them were not contented with this seldom attendance upon God in his Tabernacle, or Temple, and desired more intirely and constantly to devote himself to Gods service there, he was permitted so to do, because this was an eminent act of piety joyned with self-denyal to part with those great conveniencies which he could and did enjoy in the City of his possession, and to oblige himself to more constant and laborious work about the Sacrifices, &c.