Eretz Yisrael is praised in the Torah as a land rich in seven varieties of grains and fruits: wheat, barley, grapes, figs, pomegranates, olives and dates.
Because of their connection with the land these items of food require a special blessing after they have been consumed, even if they grew outside Eretz Yisrael.
Our Talmudic Sages also saw in each of these seven items mentioned a hint to some halachic tradition which Moshe received at Mount Sinai but is not explicitly stated in the Torah.
We thus see in these "special seven" the triangle which is formed by the Torah of Israel, the Land of Israel and the People of Israel.
