Feast of FirstFruits

Under the LAW, first fruits referred to offerings to God: Be it from labours, harvest, cattle, meat (food), fruit, honey, oil, wine, family etc. The Israelites were to put God first in all things.

Exodus 23:16 And the feast of harvest, the firstfruits of thy labours, which thou hast sown in the field: and the feast of ingathering, which is in the end of the year, when thou hast gathered in thy labours out of the field.

See other mentions of FIRSTFRUITS in: Exodus 23:19, Exodus 34:22, Exodus 34:26, Leviticus 2:12, Leviticus 2:14, Leviticus 23:10, Leviticus 23:17, Leviticus 23:20, Numbers 18:12, Numbers 28:26 and
Deuteronomy 26:10

An example of this is found in :
2 Kings 4:42 And there came a man from Baalshalisha, and brought the man of God bread of the firstfruits, twenty loaves of barley, and full ears of corn in the husk thereof. And he said, Give unto the people, that they may eat.
Other examples are found in: 2 Chronicles 31:5, Nehemiah 10:35,
Nehemiah 10:37, Nehemiah 12:44 and Nehemiah 13:31

Proverbs 3:9 Honour the LORD with thy substance, and with the firstfruits of all thine increase:

More Old Testament references to understand First Fruits: Jeremiah 2:3,
Ezekiel 20:40 and Ezekiel 44:30
Ezekiel 48:14
And they shall not sell of it, neither exchange, nor alienate the firstfruits of the land: for it is holy unto the LORD.

The Apostle Paul used the teaching of firstfruit to illustration the believer’s relationship to God:
Romans 8:23 And not only they, but ourselves also, which have the firstfruits of the Spirit, even we ourselves groan within ourselves, waiting for the adoption, to wit, the redemption of our body.
Romans 16:5 Likewise greet the church that is in their house. Salute my well-beloved Epaenetus, who is the firstfruits of Achaia unto Christ.
1 Corinthians 15:20 But now is Christ risen from the dead, and become the firstfruits of them that slept.
1 Corinthians 15:23 But every man in his own order: Christ the firstfruits; afterward they that are Christ’s at his coming.
1 Corinthians 16:15 I beseech you, brethren, (ye know the house of Stephanas, that it is the firstfruits of Achaia, and that they have addicted themselves to the ministry of the saints,)

James writing to Jewish Believer’s:
James 1:18 Of his own will begat he us with the word of truth, that we should be a kind of firstfruits of his creatures.

The 144,000 are the firstfruits during the Tribulation.
Revelation 14:4 These are they which were not defiled with women; for they are virgins. These are they which follow the Lamb whithersoever he goeth. These were redeemed from among men, being the firstfruits unto God and to the Lamb.

The feasts given to Israel were given to teach Spiritual Truths, then and now.