Halakhah sa Mga Awit 55:19: Mishneh Torah, Prayer and the Priestly Blessing & Kitzur Shulchan Arukh

Congregational prayer is always heard [by the Almighty]. Even if there are sinners among them, the Holy One, blessed be He, does not reject the prayer of a multitude. Hence, a person should associate himself with the congregation, and never recite his prayers in private when he is able to pray with the congregation. One should always attend Synagogue, morning and evening; for only if recited in a synagogue, are one's prayers heard at all times. Whoever has a synagogue in his town and does not worship there is called a bad neighbour.

You should make a serious effort to pray with a congregation, as it is written; "As for me, may my prayer to You Hashem be at a favorable time."¹³Psalms 69:14. When is the time favorable? When the congregation prays together. It is [also] written: "Thus said Hashem; at a favorable time I have answered you."¹⁴Isaiah 49:8. The Holy One blessed is He never disdains the prayer of the multitude even though there are sinners in their midst, as it is written: "Behold, Hashem is mighty, (meaning He is the God of the multitude) yet He does not despise anyone."¹⁵Job 36:5. In Hebrew, kabbir also means many. It is [also] written: "He has redeemed my soul in peace from impending battle for the sake of the many that were with me."¹⁶Psalms 55:19.