Musnad Ahmad 1012:9

'Affan narrated to us, Hammad narrated to us, Thabit al-Bunani and Humayd informed us, from Anas ibn Malik, from 'Ubadah ibn al-Samit, that the Prophet (peace and blessings of Allah be upon him) went out one night to his companions, intending to inform them about the Night of Decree (Laylat al-Qadr). He mentioned the hadith, except that he said: "Seek it in the last ten nights, on the ninth, or the seventh, or the fifth."