Musnad Ahmad 25:887

'Abd al-Samad and 'Affan narrated to us, they said: Thabit narrated to us, Hilal narrated to us, from 'Ikrimah, from Ibn 'Abbas, who said: "The Messenger of Allah (peace and blessings of Allah be upon him) performed Qunut for a consecutive month in the Dhuhr, 'Asr, Maghrib, 'Isha, and Fajr prayers, at the end of every prayer, when he said: 'Sami' Allahu liman hamidah' (Allah hears those who praise Him), in the last rak'ah, supplicating against them—against a tribe from Banu Sulaym, against Ri'l, Dhakwan, and 'Usayyah—and those behind him would say 'Amin.' He had sent them to invite them to Islam, but they killed them." 'Affan said in his narration: He said: And 'Ikrimah said: "This was the beginning of the Qunut."