John Calvin Commentary Deuteronomy 26:1

"And it shall be, when thou art come in unto the land which Jehovah thy God giveth thee for an inheritance, and possessest it, and dwellest therein," — Deuteronomy 26:1 (ASV)

And it shall be when thou art come. The Israelites are commanded to offer their first-fruits for the same reason they were to pay the tribute for every soul; namely, that they might confess that they themselves, and all that they had, belonged to God.

The only distinction was this: the tribute was a symbol of their emancipation, enabling them to acknowledge themselves as free, having been redeemed by the special mercy of God. By the first-fruits, however, they testified that the land was tributary to God. They further acknowledged that they were masters of it by no other title than as tenants at will, so that the direct sovereignty and property of it remained with God alone.

This, then, was the object of the first-fruits: that they might renew every year the recollection of their adoption. This was because the land of Canaan was given to them as their special inheritance, in which they were to worship God in piety and holiness. At the same time, they were to reflect that God did not feed them indiscriminately, like the Gentiles, but like children; which is why their food was also sacred.

However, we will have to speak again elsewhere of the first-fruits, since they were a part of the oblations. Yet it was necessary to insert their main object here. This was so that we might know they were appointed to be offered by the people in pious acknowledgment that their food was received from God, and to show that, being separated from other nations, they were dependent upon the God of Israel alone.