Musannaf Ibn Abi Shayba 27:295

Abdullah ibn Numayr narrated to us, from Amr ibn Maymun, from his father, who said: A man said to Umar ibn al-Khattab, "I have not seen anyone like you." He said, "Have you seen Abu Bakr?" He said, "No." He said, "If you had said 'yes, I have seen him,' I would have beaten you painfully."