28 Sivan, 5769 Vol. 10, No. 34 Parashas Shelach
The Ralbag (Shelach Toeles 8) explains a reason for giving the separated portion of challah, as well as other gifts, to the kohanim: Hashem wanted the kohanim to be free from worldly concerns and obligations. This would allow them to study the Torah and to understand its secrets in order to teach the Torah and its laws to the people of Israel. By commanding the rest of the Jewish people to provide the kohanim with a steady and reliable source of bread and sustenance, Hashem ensured that the kohanim will have the independence from mundane concerns and be able to devote themselves to learning and teaching.