Numbers 18:1-7 King James Version (KJV)
18 And the LORD said unto Aaron, Thou and thy sons and thy father's house with thee shall bear the iniquity of the sanctuary: and thou and thy sons with thee shall bear the iniquity of your priesthood.
2 And thy brethren also of the tribe of Levi, the tribe of thy father, bring thou with thee, that they may be joined unto thee, and minister unto thee: but thou and thy sons with thee shall minister before the tabernacle of witness.
3 And they shall keep thy charge, and the charge of all the tabernacle: only they shall not come nigh the vessels of the sanctuary and the altar, that neither they, nor ye also, die.
4 And they shall be joined unto thee, and keep the charge of the tabernacle of the congregation, for all the service of the tabernacle: and a stranger shall not come nigh unto you.
5 And ye shall keep the charge of the sanctuary, and the charge of the altar: that there be no wrath any more upon the children of Israel.
6 And I, behold, I have taken your brethren the Levites from among the children of Israel: to you they are given as a gift for the LORD, to do the service of the tabernacle of the congregation.
7 Therefore thou and thy sons with thee shall keep your priest's office for everything of the altar, and within the vail; and ye shall serve: I have given your priest's office unto you as a service of gift: and the stranger that cometh nigh shall be put to death.

Numbers 18:1-7Amplified Bible (AMP)

18 And the Lord said to Aaron, You and your sons and your father’s house with you shall bear and remove the iniquity of the sanctuary [that is, the guilt for the offenses which the people unknowingly commit when brought into contact with the manifestations of God’s presence]. And you and your sons with you shall bear and remove the iniquity of your priesthood [your own unintentional offenses].
2 And your brethren also of the tribe of Levi, the tribe of your [fore]father, bring with you, that they may be joined to you and minister to you; but only you and your sons with you shall come before the Tent of the Testimony [into the Holy Place where only priests may go and into the Most Holy Place which only the high priest dares enter].
3 And the Levites shall attend you [as servants] and attend to all the duties of the Tent; only they shall not come near the sacred vessels of the sanctuary or to the brazen altar, that they and also you [Aaron] die not.
4 And they shall be joined to you and attend to the duties of the Tent of Meeting—all the [menial] service of the Tent—and no stranger [no layman, anyone who is not a Levite] shall come near you [Aaron and your sons].
5 And you shall attend to the duties of the sanctuary and attend to the altar [of burnt offering and the altar of incense], that there be no wrath any more upon the Israelites [as in the incident of Korah, Dathan, and Abiram].
6 And I, behold, I have taken your brethren the Levites from among the Israelites; to you they are a gift, given to the Lord, to do the [menial] service of the Tent of Meeting.
7 Therefore you and your sons with you shall attend to your priesthood for everything of the altar [of burnt offering and the altar of incense] and [of the Holy of Holies] within the veil, and you shall serve. I give you your priesthood as a service of gift. And the stranger [anyone other than Moses or your sons, Aaron] who comes near shall be put to death.

Amplified Bible (AMP) Copyright © 1954, 1958, 1962, 1964, 1965, 1987 by The Lockman Foundation

These are my thoughts, please share yours.

1 It was Aaron and his sons burden to be the priests this was a very important job to do and God left it for them, even though Korah tried to take that spot it was for Aaron’s line that is until Christ came and became the ultimate sacrifice for us.

2 The Levites were all servants within the temple. The temple work was only for those who were descendents of Levi and Aaron could choose his helpers as could his sons this could have been Korah if he would wait on what God wanted he could have been the right hand man to the priest.

3 There was only a few things reserved for the high priests but the other things could have been done by all the Levites,

4 They were to aid the priests in all their work but they should not allow strangers to come to the temple, thru Christ we all can serve and are all welcome to come in.

5 The sacrifices would prevent God’s wrath on them as a result of their sin, we are prevented from God’s wrath because of His sacrifice upon the cross, we come by faith.

6 The Levities gift was not land but service to the Lord thru Christ we can gain the chance to serve Him as well, a true blessing.

7 This priest would remain until Christ died when God ripped the veil, and doing with the separation between us and Him.