(3) باب صِفَةِ الْوُضُوءِ وَكَمَالِهِ
Humran, the freed slave of 'Uthman said:
I saw Uthman call for a vessel (of water) and poured water over his hands three times and then washed them. Then he put his right hand in the vessel and rinsed his mouth and cleaned his nose. Then he washed his face three times and his hands up to the elbow three times; then wiped his head, then washed his feet three times. Then he said that the Messenger of Allah (ﷺ) had said: He who performed ablution like this ablution of mine and offered two raklahs of prayer without allowing his thoughts to be distracted, all his previous sins would be expiated.
Reference: Sahih Muslim 226b
In-book reference: Book 2, Hadith 6
USC-MSA web (English) reference(deprecated numbering scheme): Book 2, Hadith 437