Responding to Another Minyan

Question: Occasionally, I daven in a shul that has multiple minyanim going on at the same time and I can hear another minyan clearly while I am davening. Is it correct to respond to their kaddish and kedusha, etc?

Answer: The Gemara (Pesachim 85b) teaches that even an iron wall does not act as a barrier for tefilla. Thus, the Shulchan Aruch (OC 55:20) writes that one may respond to kaddish and kedusha from another room. The Rema (OC 125:1) writes that if one walks into a shul while they are saying kedusha¸ they must join in even if they have already said it.

R’ Chaim Kanievsky (quoted in Ishei Yisrael 24:n62) maintains that one who is davening and hears kedusha from another minyan needs to respond. R’ Eliezer Waldenberg (Tzitz Eliezer 11:3; 12:49:4) quote opinions that even the chazzan would have to respond to the other minyan (see Yabia Omer OC 9:3).

Nonetheless, R’ Ephraim Greenblatt (Rivevos Ephraim 1:89:2) writes that according to R’ Yosef Shalom Elyashiv and others, one would only respond to kedusha in one’s own minyan, especially if doing so would disrupt one’s concentration. This would even apply to one saying pesukei dezimra (See Shearim Metzuyanim Behalacha 20:1). Similarly, R’ Shmuel Wosner (Shevet Halevi 9:43) and R’ Moshe Sternbuch (Teshuvos Vehanhagos 2:74) write that while one is allowed to answer to kedusha, one does not need to do so, particularly if it will distract them from their davening.

Likewise, R’ Waldenberg writes that when part of one minyan, one would not need to respond to any other, following the rule of haosek bemitzva, patur min hamitzva, one who is involved in one mitzva is exempt from performing another simultaneously. One may respond to kedusha and barechu if they wish (see Ishei Yisrael 24:16; 28). Nonetheless, he stresses that one should try one’s utmost to daven in a minyan where one cannot hear other minyanim concurrently.

In conclusion, one may answer kedusha and barechu, etc. to another minyan if it will not distract one from one’s own davening. One should avoid this situation where possible by davening in a place where they are less likely to be disturbed from outside.