Under the Law of Moses, God told Israel to offer its first and best to God.
In the Law of Moses, GOD gave several instructions about "first's." Israelites were instructed to give or redeem these firsts:
28 You shall not delay to offer the first of your threshing floor and fruit press. The firstborn of your sons you shall give to Me. 29 Likewise you shall do with your calf, sheep, and donkey. It shall be with its mother seven days; on the eighth day you shall give it to Me.
(Exodus 22:28b-29 OSB)
19 All that open the womb are Mine: every male firstborn among your livestock, of oxen or sheep. 20 But the firstborn of a donkey you shall redeem with a sheep, and if you will not redeem it, you shall pay a price. All the firstborn of your sons you shall redeem, and none shall appear before Me empty-handed.
(Exodus 34:19-20 OSB)
19 The first of the first fruits of your land you shall bring into the house of the Lord your God.
(Exodus 23:19a OSB)
19 “All the firstborn males that come from your oxen and sheep you shall sanctify to the Lord your God; you shall do no work with the firstborn young bull, nor shear the firstborn of your sheep. 20 You and your household shall eat it before the Lord year by year in the place the Lord your God chooses. 21 But if there is a defect in it, if it is lame or blind or has any serious defect, you shall not sacrifice it to the Lord your God. 22 You may eat it within your cities; the unclean and the clean person alike may eat it, as if it were a gazelle or a deer. 23 Only you shall not eat its blood; you shall pour it on the ground like water.
(Deuteronomy 15:19-23 OSB)
There were multiple reasons for these instructions. One was to provide for the priests who were serving (and therefore could not farm or supply for their own needs).
Another reason was that these actions reminded Israel that their blessings came from GOD. GOD had told Israel that Israel would be blessed as long as they followed and served Him, and that they would be cursed and poor when they deserted Him. In this manner, these firstfruit offerings served as a means of mental accounting of the volume of blessings the individual had received. When there was much received, there was much to offer to GOD. And vice versa.