This Torah reading begins by charging the Jews to fulfill the mitzvah of bikkurim, the first fruits, when they "come into Eretz [Yisrael]."
A Jew must realize that when he grows produce in his field, it is not his alone. Instead, the field and its produce - and indeed, all existence - belongs to G-d. In recognition of this fact, before benefiting from them himself, the Jew takes his first fruits and brings them to Jerusalem as an offering to G-d.
As mentioned, the Torah requires this command to be fulfilled when the Jews "come into Eretz [Yisrael]." Nevertheless, our Sages explain that this commandment did not become incumbent upon our people until the entire land was divided among the tribes and each person received his ancestral heritage.
Implied is a profound lesson regarding the bonds of unity which tie our people together: Until every individual receives his portion of the land, none of the people - even one who had been living on his ancestral portion for many years - could be considered as having "come into Eretz [Yisrael]."