The Torah commands in Parashat Shoftim (Debarim 18:4) that we must give the first portion of our grain, grapes and olives to a Kohen, an obligation known as “Teruma Gedola.”
On the level of Torah law, there is no minimum required amount for fulfilling this obligation. In the Talmud’s words, “Afilu Hita Ahat Poteret Et Ha’keri” – even a single stalk of grain suffices to permit an entire heap of produce. The Sages, however, enacted that the average person should designate one-fiftieth – or 2 percent – of the produce as Teruma. Some suggest that this percentage is alluded to by the word “Teruma,” which may be read as “Tereh Me’a” – “two one-hundredths,” or one-fiftieth.
The Sefer Ha’hinuch writes that the Torah introduced this Misva because grain, wine and oil are the primary staple foods. In order for us to remember that everything in the world belongs to G-d, and all our blessings have been given to us by Him, the Torah required giving a portion of these basic staples to His servants, the Kohanim who work in the Bet Ha’mikdash. Before we enjoy the produce, we first designate a portion for the ministers in the Mikdash, so we are mindful of the fact that everything we have has been graciously given to us by Hashem. This is why Torah law requires giving even just a single stalk – because the objective is the reminder that everything belongs to G-d, and not giving a specific quantity. Nevertheless, the Sages enacted that a larger portion be given in order for this Misva to make a stronger impression upon us.
Although the Torah obligation of Teruma applies only to grain, grapes and olives, the Sages expanded the obligation to include all agricultural products, as long as it did not grow as Hefker (ownerless). The Gemara (Gittin 31) states that one separates Teruma through making an estimation; one does not need to take a precise measurement. Since, as mentioned, Torah law does not require any particular quantity for Teruma, one may estimate the one-fiftieth that he designates as Teruma.
It is acceptable to separate Teruma “She’lo Min Ha’mukaf” – meaning, for produce which is in a different place. One may designate a portion of one’s produce as Teruma even though the rest of the produce is not with him at that time.
One may appoint an agent to separate Teruma from his produce on his behalf, as long as the agent is Jewish.
Teruma may be eaten only by Kohanim. Both adult Kohanim and young Kohanim may partake of Teruma. A Kohen may share his Teruma with his wife and with his Abadim Kena’anim (gentile servants). He can also feed Teruma to his animals.
According to the Rambam, the Torah obligation of Teruma applies only in the Land of Israel when the Jewish People reside in the land. The Ra’abad disagrees, and maintains that even nowadays, the Teruma obligation applies in the Land of Israel on the level of Torah law, and not merely Mi’de’rabbanan (by force of Rabbinic enactment). The Sages expanded the Teruma obligation to certain other countries near Eretz Yisrael, such as Babylonia, the lands of Amon and Moab, and Egypt. This Misva does not apply at all, not even Mi’de’rabbanan, in other places.
The Sefer Ha’hinuch warns that one who transgresses this affirmative command, and fails to separate Teruma from his produce, is deserving of harsh punishment.