Sahih al-Bukhari 158

It is reported from Humran, the mawla of 'Uthman, that he saw 'Uthman ibn 'Affan call for a container of water which he poured over his hands three times, washing them. Then he put his right hand in the vessel and rinsed out his mouth and cleaned his nose by sniffing up water and blowing out. Then he washed his face three times and he washed his forearms to the elbows three times. Then he wiped his head and washed his feet to the ankles three times. Then he said, "The Messenger of Allah, may Allah bless him and grant him peace, said, 'Whoever does wudu' like this and then prays two rak'ats in which he does not become distracted will have his past wrong actions forgiven.' 'Urwa related from Humran, "When 'Uthman had done wudu', he said, 'I will tell you a hadith which I would not have told you if it had not been for a certain ayat. I heard the Prophet, may Allah bless him and grant him peace, say, "If a man does wudu' and does it well and prays, Allah will be forgiven everything that he does between then and the time when he prays the next prayer."'" 'Urwa said that the ayat was, "those who conceal the clear signs We have sent down" . (2:159) XXIV: On cleaning the nose with water by sniffing up and blowing out again in wudu' 'Uthman, 'Abdullah ibn Zayd and Ibn 'Abbas related it from the Prophet, may Allah bless him and grant him peace.