Your cousin came to me — he meant Al-Hasan bin Muhammad Al-Hanafiyyah — he said: How is the ghusl of janabah performed? I said: The Prophet ﷺ used to take water in his palms three times and pour it on his head, then pour water over his entire body. Al-Hasan said to me: I am a man with a lot of hair. I said: The hair of the Prophet ﷺ was much more than yours.
حَدَّثَنَا أَبُو نُعَيْمٍ، قَالَ حَدَّثَنَا مَعْمَرُ بْنُ يَحْيَى بْنِ سَامٍ، حَدَّثَنِي أَبُو جَعْفَرٍ، قَالَ
قَالَ لِي جَابِرٌ أَتَانِي ابْنُ عَمِّكَ يُعَرِّضُ بِالْحَسَنِ بْنِ مُحَمَّدٍ ابْنِ الْحَنَفِيَّةِ قَالَ كَيْفَ الْغُسْلُ مِنَ الْجَنَابَةِ فَقُلْتُ كَانَ النَّبِيُّ صلى الله عليه وسلم يَأْخُذُ ثَلاَثَةَ أَكُفٍّ وَيُفِيضُهَا عَلَى رَأْسِهِ، ثُمَّ يُفِيضُ عَلَى سَائِرِ جَسَدِهِ. فَقَالَ لِي الْحَسَنُ إِنِّي رَجُلٌ كَثِيرُ الشَّعَرِ. فَقُلْتُ كَانَ النَّبِيُّ صلى الله عليه وسلم أَكْثَرَ مِنْكَ شَعَرًا.
Reference: Sahih Al Bukhari 256