Musannaf Ibn Abi Shayba 19:148

Abu Bakr narrated to us, he said: Ibn Fudayl narrated to us, from Mutarrif, from Amir, who said: A Muslim and a Jarmaqani came to me, and each of them had slandered the other. So I flogged the Jarmaqani and left the Muslim. Then he (the Jarmaqani) went to Umar ibn Abd al-Aziz and mentioned that to him, and he said: "You did well."