Deuteronomy 18:3-9

And this shall be the priests’ due from the people, from them that offer a sacrifice, whether it be ox or sheep, that they shall give unto the priest the shoulder, and the two cheeks, and the maw. The first-fruits of thy grain, of thy new wine, and of thine oil, and the first of the fleece of thy sheep, shalt thou give him. 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. 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; then he shall minister in the name of Jehovah his God, as all his brethren the Levites do, who stand there before Jehovah. They shall have like portions to eat, besides that which cometh of the sale of his patrimony. When thou art come into the land which Jehovah thy God giveth thee, thou shalt not learn to do after the abominations of those nations.