كتاب الحيض
3  
The Book of Menstruation
(11)
Chapter: It is recommended to pour water over the head, and elsewhere, three times
(11)
باب اسْتِحْبَابِ إِفَاضَةِ الْمَاءِ عَلَى الرَّأْسِ وَغَيْرِهِ ثَلاَثًا ‏
Sahih Muslim 329

Jabir b. 'Abdullah reported:

When the Messenger of Allah (ﷺ) took a bath because of sexual intercourse, he poured three handfuls of water upon his head. Hasan b. Muhammad said to him (the narrator): My hair is thick. Upon this Jabir observed. I said to him: O son of my brother, the hair of the Messenger of Allah (ﷺ) was thicker than your hair and these were more fine (than yours).
وَحَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنَا عَبْدُ الْوَهَّابِ، - يَعْنِي الثَّقَفِيَّ - حَدَّثَنَا جَعْفَرٌ، عَنْ أَبِيهِ، عَنْ جَابِرِ بْنِ عَبْدِ اللَّهِ، قَالَ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم إِذَا اغْتَسَلَ مِنْ جَنَابَةٍ صَبَّ عَلَى رَأْسِهِ ثَلاَثَ حَفَنَاتٍ مِنْ مَاءٍ ‏.‏ فَقَالَ لَهُ الْحَسَنُ بْنُ مُحَمَّدٍ إِنَّ شَعْرِي كَثِيرٌ ‏.‏ قَالَ جَابِرٌ فَقُلْتُ لَهُ يَا ابْنَ أَخِي كَانَ شَعْرُ رَسُولِ اللَّهِ صلى الله عليه وسلم أَكْثَرَ مِنْ شَعْرِكَ وَأَطْيَبَ ‏.‏
Reference : Sahih Muslim 329
In-book reference : Book 3, Hadith 65
USC-MSA web (English) reference : Book 3, Hadith 642
  (deprecated numbering scheme)