Yahya bin Abi Kathir يحيى بن أبي كثير الطائي · The Book on Purification

"The Prophet prohibited that a man should touch his penis with his right hand."

"Allah's Messenger vomited so he performed Wudu." So I met Thawban in a Masjid in Damascus, and I mentioned that to him. He said: 'He told the truth, I poured the water for his Wudu."