Midrash su Salmi 69:14

R. Isaac said to R. Nachman: "Why did not the master come to the synagogue to pray?" "Because I was not feeling well," answered R. Nachman. "The master should have gathered ten in his house and then prayed," said R. Isaac. "It was too hard a task for me," said R. Nachman. "If so," remarked R. Isaac, "then why did not the master direct the Sexton to inform him when the public pray? [so that he might pray at that time?]" "Why are you so particular about it?" asked R. Nachman, "Because," said R. Isaac, "R. Jochanan in the name of R. Simon b. Jochai said: (Fol. 8a) 'What is meant by the passage (Ps. 69, 14.) But as for me, I direct my prayer unto Thee, O Lord, in a time of favor. When is it a time of favor? It is when the community at large prays.'" R. Jose, the son of Chanina said: "We infer it from this, (Isa. 49, 8.) Thus hath said the Lord, in the time of favor have I answered thee." R. Chanina said: "We derive it from this, (Job 36, 5.) Behold, God is mighty and despiseth no one, and it is written (Ps. 55, 19.) He delivered my soul in peace from the battle against me; for in multitudes are they (contending) with me." We have also a Baraitha to the same effect, R. Nathan said: "Whence do we know that the Holy One, praised be He! despiseth not the prayers of a community? It is written (Job 36, 5.) Behold God, many He doth not despise, and it is written (Ps. 55, 19.) He delivereth my soul in peace from the battle against me; for in multitudes, etc., i.e., the Holy One, praised be He! says: 'When any one occupies himself with the study of the Torah and the practice of loving kindness I consider as if he delivered me and my children from the nations.' "

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