The Holy Ambassadors of Peace
Over 3,300 years ago the nation of Israel received the Torah on the night of Shavuot, on the Mount Sinai. This event was accompanied with many miracles, lightning and thunder. Hashem has come down upon the mountain and gave us the Torah - it was a transfer from spiritual to physical realm or merging of the spiritual and the physical domains. This continues to happen every day, in different communities across the world.
Every day in the morning services in the Sefardi synagogues, the cohanim bless the congregants. Says Rav Yosef Karo, that the cohanim should turn their faces and hands from side to side, which the Mishna Berura (168) explains as symbolically "spreading" the blessing over the people. In a way, the cohen is acting like a conductor or an intermediary between Hashem and the community, raining the blessings from the above.
The trait of peace belongs to Aharon HaCohen and to his descendants - who are ohev shalom v'rodef shalom, the lovers and pursuers of peace, and to the cohanim of every generation till our times. Their unique ability to strengthen the broken relationships in the nation, something that has been passed down to them from Aharon HaCohen, has made them The Holy Ambassadors of Peace.
As the kohanim bless the community in the synagogues - they are emulating Hashem - just like Hashem was able to merge the spiritual and physical domains together and thus elevate the united nation of tribes to the level of prophets on Shavuot, so are the kohanim doing the same - unite the nation and bring down the spiritual blessings and rain it on the people, families and the world.
The only issue is, when those that choose to cause harm to others be it by speaking or doing evil that are present in the minyan or outside of it, prevent their own physical bodies to accept the spiritual blessings - thus doing disservice to themselves. On top of it, if the kohen is not following in the footsteps of Aaron HaCohen, and he is aware of the problems that exist in the community and he has not done anything about it in the past and is not working on implementing peace in the present, it puts him in the position where it would be hard for him to bring down the blessings for the community, thus making it hard for the whole minyan to raise their prayers to Heaven.
Why is it so important to strive for the unity inside the community, and in the nation as a whole?
Because when we have the unity - then we have more blessings rain down upon us, our families, and the world. Once united, we can stand on Shavuot or any other day - one in heart and body, like in the days of old - together shoulder to shoulder serving One and True G-d.
Shmuel Katanov