Musannaf Ibn Abi Shayba 1:1614

Abu Bakr narrated to us, he said: Abu Mu'awiyah narrated to us, from al-A'mash, from Ibrahim, from 'Abd al-Rahman ibn Yazid, he said: They said to Salman, "Has your Prophet taught you everything, even how to defecate?" He said, "Yes, he has forbidden us from cleaning ourselves with the right hand."