Sunan Ibn Majah, Chapter: The Chapters of Purification and its Sunnah

(the freed slave of Uthman bin Affan) "I saw Uthman bin Affan sitting in Maqaid.* He called for water and he performed ablution, then he said: 'I saw the Messenger of Allah (saw) sitting in this place where I am sitting, performing ablution as I have done. Then he said: "Whoever performs ablution as I have done, his previous sins will be forgiven." And the Messenger of Allah (saw) said: "And do not be conceited (due to this great virtue)." (Sahih) Another chain with similar wording. *A place in Al-Madinah near the mosque where people used to sit to discuss things.