Prayer (Kitab Al-Salat): Detailed Injunctions about Witr
Dawud :: Book 8 : Hadith 1424
Narrated Ubayy ibn Ka'b:
Al-Hasan reported: Umar ibn al-Khattab gathered the people (in tarawih prayer) behind Ubayy ibn Ka'b (who led them). He used to lead them for twenty days (during Ramadan, and would not recite the supplication except in the second half of it (i.e. Ramadan). When the last ten days remained, he kept away from them, and prayed in his house. They used to say: Ubayy ran away.