Numbers 18:12-16

All the best of the fresh oil and all the best of the fresh wine and of the grain, the first fruits of what they give to the Lord, I have given them to you.

The first ripe fruits of all that is in their land, which they bring to the Lord, shall be yours; everyone of your household who is clean may eat it.

Everything banned from secular use in Israel shall be yours.

Every firstborn of the womb of all flesh, whether human or animal, which they offer to the Lord, shall be yours; however you must redeem the human firstborn, and the firstborn of unclean animals you shall redeem.

As to their redemption price, from a month old you shall redeem them, by your assessment, five shekels in silver by the shekel of the sanctuary, which is twenty gerahs.