It is narrated from Hazrat Anas (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) recited Qunoot Nazilah after bowing in the Fajr prayer for a month and kept invoking curses upon the tribes of Ri'l, Dhakwan, and 'Usayyah, who had disobeyed Allah and His Messenger.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 13952