Musnad Abu Ya'la al-Mawsili 148:11

Abu Bakr ibn Abi Shaybah narrated to us, Mu'adh ibn Mu'adh narrated to us, from Sulayman al-Taymi, from Abu Mijlaz, from Anas ibn Malik, who said: The Messenger of Allah (may Allah bless him and grant him peace) performed Qunut for a month in the morning prayer after the bowing, supplicating against [the tribes of] Ri'l and Dhakwan.