Musnad Ahmad 928:30

'Abdullah narrated to us, Muhammad ibn Bashar Bundar narrated to me, Salm ibn Qutaybah narrated to us, Yunus ibn Abi Ishaq narrated to us, from Abu Burdah, from Zirr ibn Hubaysh, from my father, who said: "The Night of Decree (Laylat al-Qadr) is the night of the twenty-seventh."