Musnad Ahmad 572:16

'Abd al-Samad and 'Affan—the meaning being the same—narrated to us, saying: Hammad ibn Salamah narrated to us, 'Ali ibn Zayd narrated to us, from al-Hasan, that Ibn 'Amir appointed Kullab ibn Umayyah over al-Ubullah, and 'Uthman ibn Abi al-'As over his land. 'Uthman came to him and said: I heard the Messenger of Allah (peace be upon him)—'Abd al-Samad said in his narration—saying: "Indeed, there is an hour in the night during which the gates of the heaven are opened. A caller calls out: 'Is there any petitioner, that I may give him? Is there any supplicant, that I may answer him? Is there any seeker of forgiveness, that I may forgive him?'" They both said: And indeed, Dawud went out one night and said: "No one asks Allah for anything except that He gives it to him, unless he is a sorcerer or a tax collector." So Kullab called for a *qurqur* (a type of boat), boarded it, and descended to Ibn 'Amir. He said: "Take back your work." He asked: "Why?" He said: "'Uthman narrated to us such and such."