Musannaf Ibn Abi Shayba 18:1286

Abu Bakr narrated to us, he said: Shababa narrated to us, from Yahya ibn al-Husayn, he said: I heard Tariq ibn Shihab saying: Abu Bakr slapped a man one day. It was said, "We have never seen the like of today: a humiliation and a slap." Abu Bakr said, "This man came to me asking me to provide him with a mount, so I provided him with one. Then, I found him selling them. So I swore that I would not provide him with a mount—by Allah, I will not provide him with a mount—three times." Then he said to him, "Take your retribution (qisas)." But the man forgave him.