Imam al-Bukhari narrates from ‘Abdullah ibn ‘Abd al-Qari, “In one of the nights of the month of Ramadan, I went to the masjid with ‘Umar ibn al-Khattab. We saw the people in scattered groups, with individuals praying by themselves. Others were praying with a group praying behind them. ‘Umar looked at me and said, ‘In my opinion, if I can bring all these people together behind one who recites, then it would be better.’ So, he gathered them and made ‘Ubay ibn Ka‘ab lead them in prayers. I went with him another night to the masjid, and saw people all praying together behind a person reciting. ‘Umar looked at them and said, ‘Ni‘mat al-bid‘ah hadhihi (‘This is a good innovation’).’”
In the Shi‘a tradition, the recommended prayers (al-nawafil) during the month of Ramadan are performed individually.
 Sahih al-Bukhari, Vol. 1, 342