A quorum for Jewish communal prayer is ten men. We traditionally learn this from Avraham’s negotiation with G-d over the fate of Sodom, where G-d agrees that if a city has “ten righteous men,” then it can be spared divine wrath. But I think there is also another way to understand why a quorum is ten men… here goes:
What makes a righteous man? In the words of the Torah itself, righteousness is always linked to be able and willing to listen to others (as well as to G-d). The ability to hear and internalize what others say is a necessary component to being righteous and growing. I wrote about this here, pointing out that the first two men who were called “righteous” in the Torah were great listeners – but they were not even Jewish!
There are only two examples of an actual collection of ten men in the Torah, and they were not famous for listening to G-d when they acted. The first were Joseph’s brothers, who disposed of Joseph (and lied to their father about it) without ever worrying about G-d’s judgement.
The second were the spies, representing ten tribes. They came back from Canaan discouraged, and their negativity meant that the entire generation of Jews had to die in the wilderness. All because they were unwilling to listen to G-d and His advocates who pleaded for them to see things in a positive light.
Neither the brothers nor the spies were able to hear others properly. The brothers blocked themselves from allowing Joseph’s cries, just as the spies refused to hear the words of Moses, Aaron, Joshua and Caleb. They closed their hearts and minds.
So we can see Jewish prayer, the collection of ten men that pray together, as a corrective for the two sets of ten men found in the Torah, the ten men from whom we learn what not to do. When we pray we are trying to the exact opposite of the brothers and the spies: we are trying to listen, and we are trying to grow.