Aside from the issue of passing in front of somebody praying, Levites must also be wary of leaving the shul too empty. For the repetition of the Amidah prayer a minimum of six people must remain in shul (Orach Chaim 55:2; see Biur Halachah), and Levites must take stock of the situation before leaving the shul to wash Kohanim’s hands.
The door to the shul should preferably be left open, so that the Kohanim and Levites outside the shul will be able to see people inside, and therefore join in the minyan (Shulchan Aruch 55:14; see Mishnah Berurah 55:18 and 55:52).
Rabbi Moshe Sternbuch (Teshuvos Vehanhagos Vol. 3, no. 48) writes further that if less than ten men will remain in shul, a Levite should not exit the shul to wash the Kohanim’s hands. This is because the principle mitzvah of repeating the Amidah prayer was enacted for a quorum of ten, and this mitzvah takes preference over the mitzvah of Levites washing the Kohanim’s hands.
Moreover, where there are other Levites available to wash the Kohanim’s hands, Rabbi Sternbuch writes that it is better for a Levite to stay in shul (and answer amen to the blessings of the cantor) than to leave to wash hands. “The Mitzvah of answering amen is very great indeed,” and it should not missed, where other Levites can wash the Kohanim’s hands.
However, on festival days, Rabbi Sternbuch concedes that all Levites should try to wash the Kohanim’s hands, for in doing so a Levite asserts his status as part of the tribe of Levi. Rabbi Sternbuch cites that this was the practice of the Brisker Rav, who was careful to wash the Kohanim’s hands on festival days.
