The Gemara in Sotah (38a) teaches: כה תברכו בעמידה נאמר כאן כה תברכו ונאמר להלן אלה יעמדו לברך מה להלן בעמידה אף כאן בעמידה ר' נתן אומר אינו צריך הרי אומר לשרתו ולברך בשמו מה משרת בעמידה אף מברך בעמידה ומשרת גופיה מנלן דכתיב לעמוד ולשרת - “Birchas kohanim should be performed whilst standing. By birchas kohanim it says, ‘so shall you bless’ and it says later on ‘these shall stand to bless’, just like later on it means to stand, so too here it means to stand. R’ Nossan says: We don’t need this drosha, as it says by birchas kohanim ‘to serve and bless with his name’, and we learn, just like avodah needs to be performed standing, similarly birchas kohanim needs to be performed whilst standing. How do we know that the avodah needs to be done standing? It says, ‘to stand and to serve’”.
The question is, if a kohen is old and weak and unable to stand, is he allowed to perform birchas kohanim whilst sitting down, or is standing up me’akev [detrimental] and if one can’t stand it’s better that he doesn’t perform birchas kohanim?
Shevus Ya’akov
The Shu”t Shevus Ya’akov (2:1) deals with this very question. He quotes Tosfos in Sotah (38a), who quotes the Ri that says: “If a kohen performs birchas kohanim whilst sitting down, he hasn’t accomplished anything. There is a hekesh between birchas kohanim and avodah, and by avodah the Gemara in Zevochim (23b) learns that if one does the avodah sitting down, the avodah is profaned. Therefore, just like one isn’t allowed sit for avodah, similarly, one isn’t allowed to sit for birchas kohanim”. According to the Ri, if one is old and weak and unable to stand whilst performing birchas kohanim he shouldn’t perform it sitting down.
However, the Shevus Ya’akov then quotes the Rambam who learns that standing up for birchas kohanim is not me’akev. The Shevus Ya’akov concludes: An elderly person who is unable to stand should duchen whilst sitting down, as opposed to not doing it at all, and missing out on three positive commandments.
However, the Yad Aharon, and Kneses HaGedolah both rule that if a kohen must sit down, it’s better for him to refrain from performing birchas kohanim, as standing up for birchas kohanim is me’akev.
Attracting Attention
Another argument against an elderly kohan duchening sitting down, is that people will stare at him, and we find that when it comes to birchas kohanim there are a number of halachos enacted to avoid people staring at the kohanim.
Practically
Practically, the Mishnah Berurah (Orach Chaim 228:14) rules that one shouldn’t duchen whilst sitting down.
The poskim say, ideally the elderly kohen should leave shul before they get to birchas kohanim, as we are worried for the opinion of the Shevus Ya’akov (see Even Yisroel 7:10 and Shulchan Hatohar s.k. 16)
