Musannaf Ibn Abi Shayba 3:2405

Waki’ narrated to us, from al-Awza’i, from ‘Abdah, from Abu Bakr ibn ‘Amr ibn Hazm, that a man sought permission to enter upon ‘Umar during the midday heat (al-hajirah), so he kept him waiting for a long time, then he gave him permission. He said: "I was asleep during my portion (hizb) [of the Quran], so I was making it up."