Humran reported,
He reported that he saw Uthman bin Affan call for a vessel. He poured water over his hands three times and washed them, then he put his right hand into the vessel, rinsed his mouth, and sniffed water into his nose. Then he washed his face three times, his arms up to the elbows three times, wiped his head, and washed his feet up to the ankles three times.Then he said, "The Messenger of Allah ﷺ said, 'Whoever performs ablution like this ablution of mine, then prays two units of prayer without letting his thoughts wander during them, his past sins will be forgiven.'"
Azami 1581
Sahihعن حمران مولى عثمان
أنه أخبر أنه رأى عثمان بن عفان دعا بإناء، فأفرغ على كفيه ثلاث مرات فغسلهما، ثم أدخل يمينه في الإناء، فمضمض واستنشق، ثم غسل وجهه ثلاثا، ويديه إلى المرفقين ثلاث مرار، ثم مسح برأسه، ثم غسل رجليه ثلاث مرار إلى الكعبين. ثم قال: قال رسول الله ﷺ: من توضأ نحو وضوئي هذا، ثم صلى ركعتين لا يحدث فيهما نفسه، غفر له ما تقدم من ذنبه.
Bukhari narrated it in the Book of Wudu (159), and this is his wording, and Muslim narrated it in the Book of Purification (226), both through Zuhri, from Ata bin Yazid, who reported that Humran, the freed slave of Uthman, informed him.In Muslim, and also in Bukhari (164), "Then he said, 'I saw the Messenger of Allah ﷺ perform wudu like this wudu of mine, then he said...'" Ibn Shihab said, "Our scholars used to say that this wudu is the most complete way anyone performs wudu for prayer."In another narration in Muslim he said, "Shall I not show you the wudu of the Messenger of Allah ﷺ?" Then he performed wudu three times each, while there were men from among the companions of the Prophet ﷺ present with him.Abu Dawud said, "All the sahih hadiths about Uthman 
indicate that the wiping of the head was done once, for they described the wudu as being performed three times each, and when they mentioned the wiping of the head they simply said, 'and he wiped his head,' without stating any number for it, unlike everything else."I say, but Yahya bin Adam mentioned, he said, Israil narrated to us, from Amir bin Shaqiq bin Hamza, from Shaqiq bin Salama, who said, "I saw Uthman bin Affan wash his forearms three times each, and wipe his head three times, then he said, 'I saw the Messenger of Allah ﷺ do that.'"Abu Dawud said, "Waki narrated it from Israil, and he said, 'He performed wudu three times only,' meaning he did not mention the wiping being done three times."