Yahya related to me from Malik from Ismail ibn Muhammad ibn Sad ibn Abi Waqqas that Musab ibn Sad ibn Abi Waqqas said, "I was holding the Book for Sad ibn Abi Waqqas and I rubbed myself. Sad said, 'Did you touch your penis?' I replied, 'Yes,' and he said, 'Get up and do wudu.' So I got up and did wudu and then returned." [+] [Malik 002:2.16.61]