The Kohanim had two main tasks: the first was to educate and teach halachah in Israel, as it is written (Malachi 2:7), “For the kohen’s lips safeguard knowledge, and Torah is sought from his mouth.” The second was to be messengers of chesed and peace, like Aharon HaKohen, whose disciples were taught to “love peace and pursue peace, love thy fellow creatures and bring them closer to Torah” (Avot 1:12). Regarding Aharon HaKohen, Chazal relate that he knew how to make peace between friends, and between husbands and wives, and that in his merit thousands of couples remained together. Consequently, children were born to them, and they named their sons “Aharon” after him.
In order to enable the Kohanim to develop these two basic qualities, wisdom and kindness, the Torah established that Kohanim would not receive a portion of land in Israel, and that their livelihood would depend on the produce offerings and priestly gifts of the Israelites. In that way, the Kohanim would be free to learn Torah, educate the people, and guide them. Since the Yisraelim provide them with sustenance, all the people of Israel become partners in the spiritual work of the Kohanim. Due to the fact that they do not own land, and do not partake in the competition involved in earning a livelihood, they can more easily develop their love and chesed towards the entire nation.
Ahavah (love) is also the basis for Birkat Kohanim. Out of their love to the nation, the Kohanim become worthy emissaries to bless Israel in the name of Hashem. The wording of the berachah is as follows: “Who sanctified us with the holiness of Aharon and commanded us to bless His people, Israel, with love.” The poskim write that any Kohen who is hated by the congregation, or who hates the congregation, or even just one person in it, is forbidden to recite Birkat Kohanim. If he says the words out of enmity, he will bring danger upon himself. Instead, he must eliminate the animosity from his heart, or leave the synagogue before Birkat Kohanim, since its main purpose is to bless Israel with love (Mishnah Berurah 128:37; HaRav Tzvi Yehudah HaKohen, Olat Ra’ayah 2:413).