The Power of Tefillah Betzibbur Is Exclusive to Am Yisrael
‘כה אליו קרבים אלקים לו אשר גדול גוי מי כי" (ז ד) "אליו קראנו בכל אלקינו
In Maseches Rosh Hashanah (18a), the Gemara explains that this passuk is referring to tefillas rabbim, which, even after the decree is sealed, Hashem is close to the people to hear their tefillos at any time, and their tefillos can be accepted. In contrast, the passuk says (Yeshayahu 55:6) of an individual who davens for his decree to be torn up: "Dirshu Hashem behimatzo, kera’uhu behiyoso karov," the power to tear up his decree is only in Aseres Yemei Teshuvah, when Hashem is very close to him.
Harav Yitzchak Zev Soloveichik of Brisk says that in light of this, we can understand the emphasis of the passuk on the special closeness that Am Yisrael has regarding having their tefillos accepted, as compared to the nations of the world:
Although in general, prayer is effective for the nations of the world as well, as Hashem accepted the tefillah of the people of Ninveh (Yona 3:10) and Yeshayah Hanavi says (56:7): "Ki Beisi beis tefillah yikarei lechol ha’amim," still, the virtue of tefillah of the tzibbur that is accepted at all times is exclusive to Am Yisrael, because there is no concept of joining a "tzibbur" among non-Jews.
Based on this, sefer Rimon Peretz explains the term "v’oneh l’amo Yisrael be’eis shavam eilav," said in the brachah of Ga’al Yisrael: Hashem answers His people Yisrael, and only them, "when they cry to Him," in tefillas rabbim.
Chiddushei Maran R"YZ Halevi Al HaTorah; Rimon Peretz p. 23
When Is the Individual’s Request Accepted?
תדרשנו כי ומצאת אלקיך ‘ה את משם ובקשתם" (כט ד) "נפשך ובכל לבבך בכל
Why does the passuk begin with the plural "Ubikashtem" and concludes with the singular "umatzasa"?
Harav Shlomo Kluger explained: Chazal say (Rosh Hashanah 18a) that the tefillah of the tzibbur is accepted at all times, and there is no need for a special eis ratzon. From the words of Chazal there, it appears that the kavanah is not only for a request of the entire tzibbur, which is requested when said with the tzibbur. Even an individual who asks a personal request during tefillah betzibbur is guaranteed that his request will be answered. In order to teach us this concept, the passuk begins in the plural and concludes in the singular: "Ubikashtem" – during the time of tefillas rabbim "umatzasa" – that the individual request of one person is also accepted.
Harav Duber Yaffeh, the Rav of Otian and a talmid of Harav Chaim of Volozhin, explained it differently: In Maseches Rosh Hashanah (18a), Rabbi Meir asks how it is possible that two people became sick and bedridden, and they were in the same condition, yet one was healed and the other was not? He replies that the reason is because one davened a complete tefillah, meaning with kavanah, and the other did not daven a complete tefillah! Thus the passuk begins with the plural and concludes with the singular: "Ubikashtem" – even though two people are asking only one of them merits "umatzasa" – and that is the one who fulfills with all his hear the words "ki sidreshenau bechol levavcha uvechol nafshecha."
Imrei Shefer; Yesod Ohel Moed p. 29
