Deuteronomy 18:5-7

American Standard Version

⁵ For Jehovah thy God hath chosen him out of all thy tribes, to stand to minister in the name of Jehovah, him and his sons for ever.

⁶ And if a Levite come from any of thy gates out of all Israel, where he sojourneth, and come with all the desire of his soul unto the place which Jehovah shall choose; ⁷ then he shall minister in the name of Jehovah his God, as all his brethren the Levites do, who stand there before Jehovah.