If a Kohen is reciting the Pesukeh De’zimra section of the prayer service when the Hazzan reaches "Reseh" – the part of the Amida just preceding Birkat Kohanim – should he interrupt his Pesukeh De’zimra recitation to participate in Birkat Kohanim? Normally, Halacha forbids making any interruptions during Pesukeh De’zimra. Is an exception made for Birkat Kohanim, or should the Kohen simply continue reciting Pesukeh De’zimra?
The Hida (Rav Haim Yosef David Azulai, 1724-1806) addresses this question and rules that a Kohen may, in fact, interrupt Pesukeh De’zimra in order to participate in Birkat Kohanim. Even if other Kohanim are present in the synagogue, he may nevertheless join them for Birkat Kohanim. (As always, he must make an "Akira" – meaning, he must leave his place – during the Hazzan’s recitation of the Beracha of "Reseh.")
A different question arises in a case of a Kohen who recites Shema or the Berachot before or after Shema as the congregation prepares for Birkat Kohanim. The laws of Hefsek (interruption) are more stringent with regard to this section of the prayer service, thus giving rise to the question if even in this case a Kohen may interrupt his prayer to participate in Birkat Kohanim.
The Ben Ish Hai (Rav Yosef Haim of Baghdad, 1833-1909), in his work Rav Pe’alim, writes that in such a case, the Kohen should complete the paragraph which he currently recites and then go the "Duchan" for Birkat Kohanim. If the Kohen recites Shema itself, the Ben Ish Hai writes, then he should preferably complete the entire Shema before reciting Birkat Kohanim. The Ben Ish Hai rules that the Kohen may continue reciting Shema as he walks toward the "Duchan" in order to complete the recitation before he begins Birkat Kohanim.
Hacham Ovadia Yosef, however, in his work Halichot Olam, and as cited by Hacham David Yosef in Halacha Berura (vol. 6), imposes an important qualification on this ruling of the Ben Ish Hai. Namely, it applies only if there are no other Kohanim in attendance. Only in such a case does Halacha allow a Kohen to interrupt the Shema or the Berachot before or after Shema to recite Birkat Kohanim. If, however, other Kohanim are present, then he should leave the synagogue before Birkat Kohanim, and then return after Birkat Kohanim is completed.
Thus, this case differs from the case of a Kohen who recites Pesukeh De’zimra as the congregation reaches Birkat Kohanim. As mentioned earlier, a Kohen in that situation may interrupt for Birkat Kohanim even if other Kohanim are present in the synagogue.
Summary: If a Kohen is reciting Pesukeh De’zimra in the synagogue as the congregation reaches Birkat Kohanim, he may interrupt his recitation to recite Birkat Kohanim, regardless of whether or not other Kohanim are present. If he is reciting Shema or the Berachot before and after Shema, then if other Kohanim are present, he should leave the Sanctuary until after Birkat Kohanim. If he is the only Kohen present, then he should complete the paragraph he is currently reciting and may then recite Birkat Kohanim.
