وَحَدَّثَنِي مَالِكٌ، عَنْ حُمَيْدِ بْنِ قَيْسٍ، عَنْ عَطَاءِ بْنِ أَبِي رَبَاحٍ، أَنَّ عُمَرَ بْنَ الْخَطَّابِ، قَالَ لِيَعْلَى ابْنِ مُنْيَةَ وَهُوَ يَصُبُّ عَلَى عُمَرَ بْنِ الْخَطَّابِ مَاءً وَهُوَ يَغْتَسِلُ اصْبُبْ عَلَى رَأْسِي ‏.‏ فَقَالَ يَعْلَى أَتُرِيدُ أَنْ تَجْعَلَهَا بِي إِنْ أَمَرْتَنِي صَبَبْتُ ‏.‏ فَقَالَ لَهُ عُمَرُ بْنُ الْخَطَّابِ اصْبُبْ فَلَنْ يَزِيدَهُ الْمَاءُ إِلاَّ شَعَثًا ‏.‏

Malik related to me from Humayd ibn Qays from Ata ibn Abi Rabahthat 'Umar ibn alKhattab once asked Yala ibn Munya, who was pouringout water for him while he was having a ghusl, to pour some on hishead. Ya'la said, "Are you trying to make me responsible? I will onlypour it out if you tell me to do so." Umar ibn al-Khattab said, "Pour.It will only make (my head) more unkempt." Translation Not Available

Book reference: Muwatta Imam Malik Book 20 Hadith 712
Web reference: Muwatta Imam Malik Book 20 Hadith 5