Musnad Ahmad 1153:1010

'Affan narrated to us, Hammad ibn Salamah narrated to us, he said: Hisham ibn 'Urwah narrated to us, from 'Urwah, from 'Aishah, that she said: Abu Bakr entered upon us on a day of Eid, and we had two young girls singing about the day of Bu'ath, the day in which the chieftains of the Aws and the Khazraj were killed. Abu Bakr said: "O servants of Allah, the flute of Satan? O servants of Allah, the flute of Satan? O servants of Allah, the flute of Satan?" He said it three times. The Messenger of Allah, peace and blessings of Allah be upon him, said: "O Abu Bakr, indeed for every people there is an Eid, and this day is our Eid."