Musannaf Ibn Abi Shayba 19:580

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Isma’il, from ‘Isa ibn Abi ‘Azzah, from al-Sha’bi, he said: I witnessed him, and he struck a man who had slandered a man, while he was in a shirt, and he did not strike him in the mosque.