The Beis Aharon writes: "I have received the following rule: When one davens with a minyan, the Shechinah is there, and it accomplishes and corrects all matters, just as it is when the greatest tzaddik of the generation davens."
We see the power of a minyan in halachah. A great tzaddik cannot say kedusha when he is alone. Even if the nine greatest tzaddikim of our nation daven together, they still cannot say kaddish or chazoras hashatz. Yet, a minyan of simple people can say kedushah and kaddish, etc. This proves the uniqueness of a minyan, which even the greatest tzaddikim cannot compare to.
The Yaaras Devash (Vol.2 Derush 9) teaches that Esther told Mordechai that he needed to daven with a minyan to bring salvations.
It states (Esther 2:5): איש יהודי היה בשושן הבירה ושמו מרדכי – “There was a Jewish man in Shushan HaBirah (Shushan the capital) whose name was Mordechai...”
The Yaaras Devash explains that: איש יהודי היה בשושן הבירה, means that Mordechai was the only Yid living there. This is because there were two parts of Shushan: Shushan and Shushan HaBirah. Achashveirosh and the high-ranking officials lived in Shushan HaBirah, while most Yidden lived in Shushan. Mordechai, a high-ranking official also lived in Shushan HaBirah, and was the only Yid living there.
Esther told him (Esther 4:16): לך כנוס את כל היהודים – “Go, assemble all the Yidden that are found in Shushan....” to daven for Esther when she approaches Achashveirosh to plead for their lives.
The Yaaras Devash explains that Esther told Mordechai his tefillos in Shushan HaBirah were insufficient. He must gather all the Yidden and daven together.
So, we see that even the greatest people of the generation benefit from tefillah b'tzibbur. It is the most exalted form of tefillah. (R’ Elimelech Biderman)
