Musnad Ahmad 32:1781

Aswad narrated to us, Shu'bah narrated to us, from Qatadah, from Anas: "That the Prophet, peace and blessings of Allah be upon him, performed Qunut for a month, supplicating, cursing Ri'l, Dhakwan, and 'Usayyah, for they disobeyed Allah and His Messenger."