(a) Sayyiduna Khufaf bin Ima' (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) bowed. Then, after raising his blessed head from the bowing, he said: "O Allah, forgive the tribe of Banu Ghifar, and keep Banu Aslam safe. Usayyah disobeyed Allah and His Messenger. O Allah, curse Banu Lihyan, and send Your curse upon Ri'l and Dhakwan as well." Then he went down into prostration. Khalid said: The cursing of the disbelievers was done for this reason.
(b) In Sahih Muslim it is that Khufaf said: 'fa-ju'ilat' (so it was made), and it is reported from Sayyiduna Anas (may Allah be pleased with him) that he gave a ruling (fatwa) that the qunut is recited after the bowing.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3130