حَدَّثَنَا أَبُو مُصْعَبٍ، حَدَّثَنَا مَالِكٌ، عَنْ زَيْدِ بْنِ أَسْلَمَ، عَنْ إِبْرَاهِيمَ بْنِ عَبْدِ اللَّهِ بْنِ حُنَيْنٍ، عَنْ أَبِيهِ، أَنَّ عَبْدَ اللَّهِ بْنَ عَبَّاسٍ، وَالْمِسْوَرَ بْنَ مَخْرَمَةَ، اخْتَلَفَا بِالأَبْوَاءِ فَقَالَ عَبْدُ اللَّهِ بْنُ عَبَّاسٍ يَغْسِلُ الْمُحْرِمُ رَأْسَهُ ‏.‏ وَقَالَ الْمِسْوَرُ بْنُ مَخْرَمَةَ لاَ يَغْسِلُ الْمُحْرِمُ رَأْسَهُ ‏.‏ فَأَرْسَلَنِي ابْنُ عَبَّاسٍ إِلَى أَبِي أَيُّوبَ الأَنْصَارِيِّ أَسْأَلُهُ عَنْ ذَلِكَ، فَوَجَدْتُهُ يَغْتَسِلُ بَيْنَ الْقَرْنَيْنِ وَهُوَ يَسْتَتِرُ بِثَوْبٍ فَسَلَّمْتُ عَلَيْهِ فَقَالَ مَنْ هَذَا قُلْتُ أَنَا عَبْدُ اللَّهِ بْنُ حُنَيْنٍ أَرْسَلَنِي إِلَيْكَ عَبْدُ اللَّهِ بْنُ عَبَّاسٍ أَسْأَلُكَ كَيْفَ كَانَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ يَغْسِلُ رَأْسَهُ وَهُوَ مُحْرِمٌ قَالَ فَوَضَعَ أَبُو أَيُّوبَ يَدَهُ عَلَى الثَّوْبِ فَطَأْطَأَهُ حَتَّى بَدَا لِي رَأْسُهُ ثُمَّ قَالَ لإِنْسَانٍ يَصُبُّ عَلَيْهِ اصْبُبْ ‏.‏ فَصَبَّ عَلَى رَأْسِهِ ثُمَّ حَرَّكَ رَأْسَهُ بِيَدَيْهِ فَأَقْبَلَ بِهِمَا وَأَدْبَرَ ‏.‏ ثُمَّ قَالَ هَكَذَا رَأَيْتُهُ ـ صلى الله عليه وسلم ـ يَفْعَلُ ‏.‏

It wasnarrated from Ibrahim bin ‘Abdullah bin Hunain, from his father,that ‘Abdullah bin ‘Abbas and Miswar bin Makhramah disagreed atAbwa’. Abdullah bin ‘Abbas said that the Muhrim may wash hishead, and Miswar said that the Muhrim may not wash his head.Ibn ‘Abbas sent me to Abu Ayyub Al-Ansari to ask him about that, and I found him taking a bath near the well, screened with a piece of cloth. I greeted him with Salam, and he said: “Who is this?” I said: “I am ‘Abdullah bin Hunain. ‘Abdullah bin ‘Abbas sent me to you to ask you how the Messenger of Allah (PBUH) used to wash his head when he was in Ihram.” He said: “Abu Ayyub put his hand on the cloth and lowered it until his head appeared, then he said to someone who was pouring water for him, Pour water. So he poured water on his head. Then he rubbed his head with his hands, forwards and backwards, and said: ‘This is what I saw him (PBUH) doing.’” Translation Not Available

Book Ref: Sunan Ibn Majah Book 25 Hadith 2934
Web Ref:  Sunan Ibn Majah Vol 4 Book 25 Hadith 2934