Deuteronomy 18:6

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 Deuteronomy 18:8. It seems probable that the several priests were to come from their cities to the temple by turns before David's 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 entirely and constantly to devote himself to God's service there, he was permitted so to do, because this was an eminent act of piety joined with self-denial 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.