Language:
كتاب الوضوء
4  
Ablutions (Wudu')
(38)
Chapter: To pass wet hands over the whole head during ablution
(38)
باب مَسْحِ الرَّأْسِ كُلِّهِ
Sahih al-Bukhari 185

Narrated Yahya Al-Mazini:

A person asked `Abdullah bin Zaid who was the grandfather of `Amr bin Yahya, "Can you show me how Allah's Messenger (ﷺ) used to perform ablution?" `Abdullah bin Zaid replied in the affirmative and asked for water. He poured it on his hands and washed them twice, then he rinsed his mouth thrice and washed his nose with water thrice by putting water in it and blowing it out. He washed his face thrice and after that he washed his forearms up to the elbows twice and then passed his wet hands over his head from its front to its back and vice versa (beginning from the front and taking them to the back of his head up to the nape of the neck and then brought them to the front again from where he had started) and washed his feet (up to the ankles).

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يُوسُفَ، قَالَ أَخْبَرَنَا مَالِكٌ، عَنْ عَمْرِو بْنِ يَحْيَى الْمَازِنِيِّ، عَنْ أَبِيهِ، أَنَّ رَجُلاً، قَالَ لِعَبْدِ اللَّهِ بْنِ زَيْدٍ ـ وَهُوَ جَدُّ عَمْرِو بْنِ يَحْيَى ـ أَتَسْتَطِيعُ أَنْ تُرِيَنِي، كَيْفَ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يَتَوَضَّأُ فَقَالَ عَبْدُ اللَّهِ بْنُ زَيْدٍ نَعَمْ‏.‏ فَدَعَا بِمَاءٍ، فَأَفْرَغَ عَلَى يَدَيْهِ فَغَسَلَ يَدَهُ مَرَّتَيْنِ، ثُمَّ مَضْمَضَ وَاسْتَنْثَرَ ثَلاَثًا، ثُمَّ غَسَلَ وَجْهَهُ ثَلاَثًا، ثُمَّ غَسَلَ يَدَيْهِ مَرَّتَيْنِ مَرَّتَيْنِ إِلَى الْمِرْفَقَيْنِ، ثُمَّ مَسَحَ رَأْسَهُ بِيَدَيْهِ، فَأَقْبَلَ بِهِمَا وَأَدْبَرَ، بَدَأَ بِمُقَدَّمِ رَأْسِهِ، حَتَّى ذَهَبَ بِهِمَا إِلَى قَفَاهُ، ثُمَّ رَدَّهُمَا إِلَى الْمَكَانِ الَّذِي بَدَأَ مِنْهُ، ثُمَّ غَسَلَ رِجْلَيْهِ‏.‏
Reference : Sahih al-Bukhari 185
In-book reference : Book 4, Hadith 51
USC-MSA web (English) reference : Vol. 1, Book 4, Hadith 185
  (deprecated numbering scheme)