The Torah in Parashat Shelach (15:17-21) introduces the mitzva of challa, which requires giving a portion of one’s dough to a kohen. The donated portion is referred to in these verses with the term “teruma,” and explicitly compares it to terumat goren – the portion of grain donated to a kohen (15:20). As Rashi cites from the Sifrei, Chazal established on this basis a degree of parity between the obligations of teruma and challa. Specifically, Rashi writes, just as the Torah did not give any minimum required percentage for teruma, and even a single stalk suffices for the entire heap, likewise, the Torah obligation of challa does not require any minimum quantity. Nevertheless, the Sages enacted that one should donate 1/24th of the batter to a kohen, or, if one prepares baked goods commercially, to be sold, then 1/48th, as discussed by the Mishna in Masekhet Challa (2:7).
Rav Menachem Bentzion Zaks, in his Menachem Tziyon, suggests an additional insight into the comparison drawn between the obligations of teruma and challa. He notes that these donations are the first and last donations required from the grain which one produces. After the crop is harvested, one first donates teruma to a kohen, followed by the ma’aser rishon tithe to a Levi, and then, depending on the year, by either ma’aser sheni (a portion which one brings to Jerusalem and eats there) or the ma’aser ani donation to the poor. After the grain has been made into a dough, the individual is then required to separate a portion and give it to a kohen. The comparison between teruma and challa, Rav Zaks suggests, perhaps indicates that the final donation must be given just as happily and graciously as the first donation. When people are approached to donate charity, they are likely to eagerly respond the first time, but after several requests, even if they can afford additional contributions, they might become aggravated and displeased. If they agree to make a donation for the fourth time, they are likely to do so far less eagerly and enthusiastically. And so the obligation of challa is likened to the obligation of teruma – to emphasize that the fourth donation should be given just as graciously and joyfully as the first.
Rav Zaks cites in this context the prophet Malakhi’s famous promise given to those who pay the required tithes: “va-harikoti lakhem berakha ad beli dai” – “I will shower you with unlimited blessing” (Malakhi 3:10). The Gemara (Shabbat 32b) explains the phrase “ad beli dai” to mean, “ad she-yivlu siftoteikhem mi-lomar dai” – “until your lips are worn from saying, ‘Enough!’” If we are prepared to repeatedly give, and share our material blessings with others with joy and enthusiasm even after making numerous donations, then we are promised that God will repeatedly give to us, and grant us continued blessing and prosperity.