'First fruit' in the Bible

"Reuben, you're my firstborn, my strength, and the first fruit of my vitality. You excel in rank and excel in power.

Instead, he must acknowledge the firstborn of the unloved wife by giving him double of everything he owns, because he is really the first fruit of his father's strength. The right of the firstborn belongs to him."

Later on, a man arrived from Baal-shalishah, bringing the man of God some bread as a first fruit offering. He had 20 loaves of barley and ripe ears of corn in his sack. So Elisha said, "Give them to the people so they can eat."

This is what the Lord GOD showed me: Look! He was forming locust swarms as the latter plantings were just beginning to sprout. Indeed, the king had just taken his first fruit tax.