Mischna zu Schemot 23:17

These are the things that have no definite quantity: The corners [of the field]. First-fruits; [The offerings brought] on appearing [at the Temple on the three pilgrimage festivals]. The performance of righteous deeds; And the study of the torah. The following are the things for which a man enjoys the fruits in this world while the principal remains for him in the world to come: Honoring one’s father and mother; The performance of righteous deeds; And the making of peace between a person and his friend; And the study of the torah is equal to them all.

Bikkurim are brought only from the seven species. Not from dates grown on hills, nor from [the other species] grown in the valley, nor from olives that are not choice. Bikkurim are not to be brought before Shavuot. The people from Mt. Zevoim brought bikkurim prior to Atzeret (Shavuot), but they did not accept from them, on for it is written in the Torah: “And the festival of the harvest, the first-fruits of your labors, which you have sown in the field” (Exodus 23:16).