God returns to giving instructions, as we see here with the details of what the priesthood costs and the benefits of service to Aaron and his descendants.

Numbers 18

The LORD said to Aaron “You and your sons and your father’s house with you shall bear the guilt of the sanctuary: and you and your sons only shall bear the guilt of the sins of your priesthood.

2 Bring with you your brothers of the tribe of Levi, the tribe of your father,  that they may be joined to you, and minister to you: but you and your sons only shall minister before the tabernacle of witness.

3 They shall keep your charge, and the charge of all the tabernacle: only they shall not come near the vessels of the sanctuary and the altar, that neither they, nor you also, die.

4 And they shall be joined to you, and keep the charge of the tent of meeting, for all the service of the tabernacle: and a stranger shall not come nigh unto you.

5 You shall keep the charge of the sanctuary, and the of the altar, that there be no more wrath on the children of Israel.

6 I have taken your brothers 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 tent of meeting.

7 Therefore you and your sons with you shall keep your priest’s office for everything of the altar, and within the veil; and you shall serve: I have given your priest’s office to you as a service of gift: and the stranger that comes near shall be put to death.”

8 The LORD spoke to Aaron: “Behold, I have also given you the charge of my presentations offerings of all the holy things of the children of Israel; to you I have given them by reason of the anointing, and to your sons, by an ordinance forever.

9 These shall be yours of the most holy things, reserved from the fire: every offering of theirs, every grain offering, every sin offering, and every trespass offering which they give me, shall be most holy for you and your sons.

10 In the most holy place you shall eat it; every male shall eat it: it shall be holy to you.

11 And these are yours; the contributions of their gift, with all the presentation offerings of the children of Israel I have given them to you, and to your sons and to your daughters with you, by a statute forever: every one that is clean in your house shall eat of it.

12 All the best of the oil, and all the best of the wine, and of the wheat, the firstfruits which they shall offer to the LORD, I have given them to you. 

13 Whatever is first ripe in the land, which they shall bring to the LORD, shall be yours; everyone that is clean in your house shall eat of it.

14 Everything devoted in Israel shall be yours.

15 Everything that opens the womb in all flesh, which they bring to the LORD, whether it is people or animals, shall be yours: nevertheless the firstborn of man you shall surely redeem, and the firstling of unclean animals you shall redeem.

16 And those that are to be redeemed from a month old you shall redeem, according to your estimation, for the price of five shekels, after the shekel of the sanctuary, which is twenty gerahs.

17 But the firstling of a cow, a sheep, or a goat, you shall not redeem; they are holy: you shall sprinkle their blood on the altar, and shall burn their fat for an offering made by fire, for a pleasing aroma to the LORD.

18 But their meat shall be yours, as the breast of presentation and the right thigh are yours.

19 All the holy contributions, which the children of Israel offer to the LORD, I have given to you, and your sons and daughters with you, by a statute forever: it is a covenant of salt forever before the LORD to you and to your descendants.”

20 The LORD spoke to Aaron “You shalt have no inheritance in their land, neither shall you have any part among them: I am your part and your inheritance among the children of Israel.

21 Behold, I have given the children of Levi all the tenth in Israel for an inheritance, for their service which they serve in the tent of meeting.

22 The children of Israel must not come near the tent of meeting, lest they bear sin, and die.

23 But the Levites shall do the service of the tent of meeting, and they shall bear their guilt: it shall be a statute forever throughout your generations, that among the children of Israel they have no inheritance.

24 But the tithes of the children of Israel, which they offer as a contribution to the LORD, I have given to the Levites to inherit: therefore I have said to them ‘Among the children of Israel they shall have no inheritance.’”

25 The LORD spoke to Moses, saying:

26 “Speak this way to the Levites, saying to them ‘When you take the tithes from the children of Israel which I have given you for your inheritance, then you must present part of it as an offering to the LORD, even a tenth part of the tithe.

27 Your contribution shall be counted to you as though it were the grain of the threshingfloor, and as the fulness of the winepress.

28 So you shall offer a contribution to the LORD of all your tithes, which you receive of the children of Israel; and you shall give the LORD’S presentation offering to Aaron the priest.

29 Out of all your gifts you shall present every contribution of the LORD, all the best thereof, the holy part out of it.’

30 Therefore you shall say to them ‘When you have offered the best of it, then it shall be counted to the Levites as the increase of the threshingfloor, and as the increase of the winepress.

31 You shall eat it in every place, you and your household: for it is your reward for your service in the tent of meeting.

32 And you shall bear no sin by reason of it, when you have offered from it the best of it: neither shall you pollute the holy things of the children of Israel, lest you die.'”

See also: Numbers 18 in ESV, HCSB, NASB and NIV via Bible Gateway.