Numbers 18:24-27

²⁴Instead I have given to the Levites as their compensation the tithe that the Israelites give to the Lord as a contribution. That's why I told them that they wouldn't receive a share of land among the Israelites.”

²⁵The Lord told Moses,

²⁶“Talk to the Levites and explain to them, ‘When you receive from the Israelites the tithe that I have given you as your compensation, you must return part of it as an offering to the Lord: a tithe of the tithe.

²⁷Your offering will be considered as if it were the firstfruits of grain from your threshing floor or grape juice from the winepress.