The Book of Prayers (Kitab Al-Salat)
Muslim :: Book 4 : Hadith 1435
Anas b. Malik reported: The Messenger of Allah (may peace be upon him) observed Qunut for a month in the dawn prayer after ruku' and invoked curse upon Ri'l, Dhakwan, and said that 'Usayya had disobeyed Allah and His Apostle (may peace be upon him).