Humran, the freed slave of Sayyiduna Uthman (may Allah be pleased with him), says: I saw Sayyiduna Uthman bin Affan (may Allah be pleased with him) performing ablution. He poured water from the vessel onto his hands, then washed them three times, then put his right hand into the water, then rinsed his mouth and sniffed water into his nose, then washed his face three times and washed his hands up to and including his elbows, then wiped his head, then washed his right foot three times, then washed his left foot three times. Then he said: I saw the Messenger of Allah (peace and blessings be upon him) performing ablution like this, [and he (peace and blessings be upon him) said:] "Whoever performs ablution like my ablution, then prays two rak'ahs in which no bad thought arises in his heart, his past sins will be forgiven."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 217
Ata bin Yazid (may Allah have mercy on him) narrated the same meaning as the previous narration; he says: Then he put his right hand into the ablution water, then rinsed his mouth and sniffed water into his nose.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 219
It is narrated from Humran, the freed slave of Sayyiduna Uthman (may Allah be pleased with him), that Sayyiduna Uthman bin Affan (may Allah be pleased with him) called for water, then poured water from the vessel onto his hand, then washed it three times, then put his right hand into the water, then rinsed his mouth, sniffed water into his nose and blew it out, then washed his face three times and washed his hands up to and including the elbows three times, then wiped his head, then washed both feet three times. Then he said: I have seen the Messenger of Allah (peace and blessings be upon him); he used to perform ablution like this ablution of mine. Then he said: "Whoever does like this ablution of mine, then stands and prays two rak'ahs in which no bad thought arises in his heart, his previous sins will be forgiven."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 220