The Psalmist wrote, "He will regard the prayer of the destitute" (Psalms 102:17), and the Kabbalists pressed hard on the verb. Why does it say regard, and not simply hear?
Because there is a distinction, they taught, between the prayer of a single person and the prayer of a community. When a congregation prays together, their prayer enters directly before the Holy One — blessed be He. He does not first scrutinize every worshiper's deeds; He does not weigh each heart to see whether it deserves an answer. The communal prayer passes the gate on its own strength.
But when an individual stands alone before God, heaven leans close to examine. Is this heart devout? Is this person righteous? Now the prayer is subject to regard — to God's attentive, discerning look — before it is received.
This, the mystics teach, is why a person should always try to pray with the community, even when he would rather daven alone. The end of that same Psalm confirms it: "And He will not despise their prayer" (Psalms 102:17). Although some individuals in the congregation, on the strength of their own deeds, might deserve to have their prayers brushed aside, when their voices are woven into the minyan, the whole prayer is received together.
The community lifts the person who could not lift himself. That, the Kabbalists say, is one of the quietest miracles Judaism practices three times a day.
(From the 1901 Hebraic Literature anthology, drawing on Kitzur Shnei Luchot ha-Brit.)