Mitzvah 119: Neta Revay

When a tree is in its fourth year, the fruit is called "neta revay" and can only be eaten in Yerushalayim. The fourth year of a tree is the first year that the fruit can finally be eaten and so we have to go to Yerushalayim to praise Hashem, as the Pasuk says (Vayikra 19: 23-24), "When you plant fruit trees... on the fourth year all the fruit shall be holy praises for Hashem".

We thereby receive Hashem's blessing. Additionally, Yerushalayim is the headquarters of Torah study. By coming there to eat, one may learn some Torah and he or his child may even stay a while to learn Torah (Sefer Hachinuch).