Musannaf Ibn Abi Shayba 19:261

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Shu’bah, from Salamah, from al-Hasan al-‘Arani, from ‘Abd al-Rahman ibn Abi Layla: That a man had a hired servant, and he found a man with his wife under a quilt, so he struck him forty [times].