Birkat Kohanim

Hi,

It is clear that kohanim are obligated to offer a blessing in Birkat Kohanim (aka duchening); according to some, the non-kohanim present are obligated to remain present and accept that blessing.

Even according to the view that non-kohanim are obligated to accept the blessing, the opening berachah (אשר קדשנו בקדושתו של אהרן) is only upon the mitzvah of the kohanim, and not of the rest of the minyan. Therefore, the listeners could, theoretically, say "Baruch Hu uVaruch Shmo" in their response to the berachah, without that response constituting an interruption. However, we avoid this lest their be any disturbance at all in the course of Birkat Kohanim.

(Rav Moshe Feinstein, Igrot Moshe Orach Chaim 3:17)

Have a great day,
Mordechai