Muwatta Malik, Book 20, Hadith 5 (USC-MSA) ⓘ

Malik related to me from Humayd ibn Qays from Ata ibn Abi Rabah that 'Umar ibn alKhattab once asked Yala ibn Munya, who was pouring out water for him while he was having a ghusl, to pour some on his head. Ya'la said, "Are you trying to make me responsible? I will only pour it out if you tell me to do so." Umar ibn al-Khattab said, "Pour. It will only make (my head) more unkempt."

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 ‏.‏