Numbers 18:12-15

12I give you all the freshest olive oil and all the finest new wine and grain that the Israelites give to the LORD as their firstfruits. 13The firstfruits of everything in their land that they bring to the LORD will belong to you. Every ceremonially clean person in your household may eat them.

14Every devoted thing in Israel belongs to you. 15The firstborn of every womb, whether man or beast, that is offered to the LORD belongs to you. But you must surely redeem every firstborn son and every firstborn male of unclean animals.