The Tzemach Tzedek’s son, Reb Yosef Yitzchak, was a son-in-law of the great Reb Yaakov Yisrael Tsherkaser. When Reb Yaakov Yisrael asked his son-in-law about his davening [i.e., whether he davened at length or davened with the minyan], he responded that he tried to pray with a minyan. Reb Yaakov Yisrael was pleased with the answer.

Once, Reb Yaakov Yisrael sent someone to summon Reb Yosef Yitzchak to him, but the messenger found him involved in prayer. This caused Reb Yaakov Yisroel to wonder, since the minyan had already finished praying. Soon after, he again summoned his son-in-law but he was still in the middle of his prayers. This continued several times and much time elapsed. When Reb Yosef Yitzchak finished praying, Reb Yaakov Yisroel asked him: “Didn’t you tell me that you try to pray with a minyan?” Reb Yosef Yitzchak answered: “I heard from my father, in the name of the Alter Rebbe, that the concept of praying with a tzibbur (minyan) is litzbor, to gather together all the forces of the soul and all its G‑dly sparks. This takes a long time.”1

Likkutei Sichos, vol. 2, p. 477