By Rabbi Berach Steinfeld
The Gemara in Brachos, daf chof vov, amud bais teaches us that Yaakov established the tefillah of Maariv. An interesting question arises when there are people who daven at an early zman who are near others who daven with a late zman. For example, what is the halacha if Shmuel davened maariv at an early minyan before sunset and subsequently hears a late mincha minyan davening next door. May he answer kedusha with the tzibbur?
The Shailos U’tshuvos Gur Aryeh Yehuda in Orach Chaim, siman kuf vov writes that if one already davened maariv and hears kedusha from a mincha minyan, he would not be allowed to answer since it is a “tarti desasri” (contradiction.) He quotes a proof to this from the Taz in Orach Chaim, siman resh lamed vov and in the Magen Avraham in the same siman that paskens that if one arrives to Shul on Friday night after Borchu and he had not yet davened mincha, he should not daven his shmone esrei with the tzibbur while they are davening maariv because while he is davening mincha he has no shaychos with the tefilla of maariv that the tzibbur is davening. This is considered tarti desasri. The Shailos U’tshuvos Gur Aryeh Yehuda also brings a proof from the Terumas Hadeshen, siman daled that if one was already mekabel Shabbos, one may no longer daven mincha. The Shailos Utshuvos Ha’elef Lecha Shlomo in Orach Chaim, siman tzaddik daled agrees that if one davened maariv, one should not answer kedusha of mincha, but he may answer amen.
In the Shailos Utshuvos Amudei Eish in siman gimmel, seif yud tes the author argues with this premise and refutes the proof. Shabbos is different in the fact that when one is mekabel Shabbos he is in a position of holiness and therefore he may not say or do things of the weekday. In contrast, we don’t find the fact that one is mekabel the next day during the week. He therefore holds that one may answer kedusha. The Magen Gibborim in Siman resh lamed zayin, seif koton alef is medayek from the Rambam and Rashba that explain the reason we don’t have chazaras hashatz during maariv is because the tefilla of maariv is a reshus (not obligatory.) Had it not been for the reason of reshus we would have had a chazaras hashatz at maariv also; therefore, even if one already davened maariv he would be able to answer to the kedusha of mincha. Another proof is the fact that there is chazaras hashatz during Ne’ilah on Yom Kippur despite the fact that it could “patter” maariv according to the shita of Rav in Yuma, daf peh zayin. So we see that one may answer kedusha formincha even if one already davened maariv. The Eishel Avraham in siman kuf ches agrees with the above.
The Shailos Utshuvos Siach Yitzchok, siman kuf tes vov brings proof from the Meiri that one may answer kedusha. The Meiri writes in Brachos, daf chof alef, amud bais that if one finds the shaliach tzibbur starting the repetition of tefillas mincha and he is davening maariv, he may read along word for word, but he should not stop and say kedusha. This is so because one may only say kedusha in Shmone Esrei for a tefilla where he was mesaken kedusha. If we would say that one who already davened maariv may not say kedusha, then the Meiri should have said that the reason is that it is nighttime for him and he already davened the berachos of Maariv and that is why he may not say kedusha. The fact that the Meiri does not say that and just says that it would be a hefsek in the middle of the tefilla belachash shows that if he already davened he may answer kedusha.
From this consensus it would seem that it would be better not to put yourself in a position to have to answer kedusha in such a scenario, but if it does happen one should answer kedusha.