Numbers 18:2

“And to thy brethren also of the tribe of Levi, the tribe of thy father, etc.] For his father Amram was of that tribe, and so the Levites were his brethren, as he is directed to consider them; which might serve to conciliate their minds, and make them easy with respect to his enjoyment of the priesthood: bring them with thee; into the court of the tabernacle, for further they might not go: that they maybe joined unto thee: as their name of Levites signifies, persons joined and united to others, as they were to the priests: see reason of their patriarch’s name Levi in (<012934>Genesis 29:34); and minister unto thee: be assisting to the priests in killing the sacrifices, receiving the blood,…”

“thy brethren also of the tribe of Levi--The departments of the sacred office, to be filled respectively by the priests and Levites, are here assigned to each. To the priests was committed the charge of the sanctuary and the altar, while the Levites were to take care of everything else about the tabernacle. The Levites were to attend the priests as servants--bestowed on them as "gifts" to aid in the service of the tabernacle--while the high and dignified office of the priesthood was a "service of gift." "A stranger," that is, one, neither a priest nor a Levite, who should intrude into any departments of the sacred office, should incur the penalty of death.”

“Unto thee - About sacrifices and offerings and other things, according to the rules I have prescribed them. The Levites are said to minister to Aaron here, to the church, Num 16:9, and to God, Deu 10:8. They shall not contend with thee for superiority, as they have done, but shall be subordinate to thee. Thy sons with thee - Or, both to thee, and to thy sons with thee: Which translation may seem to be favoured by the following words, before the tabernacle, which was the proper place where the Levites ministered. Besides, both the foregoing words, and the two following verses, entirely speak of the ministry of the Levites, and the ministry of the priests is distinctly spoken of, Num 18:5.…”

“joined unto thee: There is a fine paronomasia in the original. Levi is desired from lawah, to join, couple, associate; hence Moses says, the Levites yillawoo, "shall be joined," or associated, with the priests. they shall conjointly perform the sacred office, but the priests shall be principal, the Levites their associates or assistants. Num 18:4; Gen 29:34 minister: Num 3:6-9, Num 8:19, Num 8:22 but thou: Num 3:10-13, Num 4:15, Num 16:40, Num 17:7; Ch1 16:39, Ch1 16:40; Ch2 30:16; Eze 44:15 Numbers 18:3”