Muwatta Malik Book 6, Hadith 4
Yahya related to me from Malik from Muhammad ibn Yusuf that as-
Sa'ib ibn Yazid said, "Umar ibn al-Khattab ordered Ubayy ibn Kab and
Tamim ad-Dari to watch the night in prayer with the people for eleven
rakas.The reciterof the Qur'an would recite the Mi'in (a group of
medium-sized suras) until we would be leaning on our staffs from
having stood so long in prayer. And we would not leave until the
approach of dawn."
Malik related to me from Ibn Shihab from Urwa ibn az-Zubayr that Abd ar-Rahman ibn Abd al-Qari said, "I went out with Umar ibn alKhattab in Ramadan to the mosque and the people there were spread out in groups. Some men were praying by themselves, whilst others were praying in small groups. Umar said, 'By Allah! It would be better in my opinion if these people gathered behind one reciter.' So he gathered them behind Ubayy ibn Kab. Then I went out with him another night and the people were praying behind their Qur'an reciter. Umar said, 'How excellent this new way is, but what you miss while you are asleep is better than what you watch in prayer.' He meant the end of the night, and people used to watch the beginning of the night in prayer."
Yahya related to me from Malik that Yazid ibn Ruman said, "The people used to watch the night in prayer during Ramadan for twenty- three rakas in the time of Umar ibn al-Khattab."