(Exodus 13:1-2 NKJV) Then the LORD spoke to Moses, saying, "Consecrate to Me all the firstborn, whatever opens the womb among the children of Israel, both of man and beast; it is Mine."
(Exodus 13:12-13 NKJV) That you shall set apart to the LORD all that open the womb, that is, every firstborn that comes from an animal which you have; the males shall be the LORD's. But every firstborn of a donkey you shall redeem with a lamb; and if you will not redeem it, then you shall break its neck. And all the firstborn of man among your sons you shall redeem.
The first must be sacrificed or redeemed.
The firstfruits must be offered.
(Proverbs 3:9-10 NKJV) Honor the LORD with your possessions, and with the firstfruits of all your increase; So your barns will be filled with plenty, And your vats will overflow with new wine.
(Exodus 23:19 NKJV) The first of the firstfruits of your land you shall bring into the house of the LORD your God.
(Genesis 4:3-5 NKJV) And in the process of time it came to pass that Cain brought an offering of the fruit of the ground to the LORD. 4 Abel also brought of the firstborn of his flock and of their fat. And the LORD respected Abel and his offering, 5 but He did not respect Cain and his offering.
The tithe must be first.
(Leviticus 27:30 NKJV) And all the tithe of the land, whether of the seed of the land or of the fruit of the tree, is the LORD's. It is holy to the LORD.
(Exodus 13:14-15 NKJV) So it shall be, when your son asks you in time to come, saying, 'What is this?' that you shall say to him, 'By strength of hand the LORD brought us out of Egypt, out of the house of bondage. And it came to pass, when Pharaoh was stubborn about letting us go, that the LORD killed all the firstborn in the land of Egypt, both the firstborn of man and the firstborn of beast. Therefore I sacrifice to the LORD all males that open the womb, but all the firstborn of my sons I redeem.