Musannaf Ibn Abi Shayba 19:814

Abu Bakr narrated to us, he said: Abd al-A’la narrated to us, from Ma’mar, from al-Zuhri, that a man from the Emigrants (Muhajirun) slandered him during the era of Umar ibn al-Khattab, and his mother had died during the Pre-Islamic period (Jahiliyyah). So Umar flogged him due to the sanctity of the Muslim.