Deuteronomy 26:6

And the Egyptians evil entreated us, and afflicted us, and laid upon us hard bondage:

The verse recalls that the Egyptians mistreated and oppressed Israel, treating them cruelly, afflicting them, and laying hard bondage and hard labor upon them. This oppression stands as part of Israel's own account of God's deliverance from Egypt. It belongs to the history of that deliverance which Israel was to remember and acknowledge with gratitude.

The affliction belongs to the account of God hearing Israel's cry and bringing them out of Egypt into the land He gave them. That deliverance and gift of the land called for gratitude expressed by offering Him the firstfruits. As part of that firstfruits instruction, offerings are to be presented with reverence and gratitude, not as though God were indebted for His blessings, but in recognition that every good thing comes from God, to give Him thanks and glory.