Musnad Ahmad 28:208

Ya'la narrated to us, Sufyan narrated to us, from Musa ibn Abi 'Aisha, from 'Amr ibn Shu'ayb, from his father, from his grandfather, who said: A Bedouin came to the Prophet, may Allah bless him and grant him peace, asking him about ablution (wudu). So he showed him three times, three times. He said: "This is the ablution. Whoever increases upon this has done evil, transgressed, and committed injustice."