The ihram and the talbiya - Section 2 Mishkat al-Masabih 2548
Arabic hadith text
وَعَنِ ابْنِ عُمَرَ أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ لَبَّدَ رَأْسَهُ بِالْغِسْلِ. رَوَاهُ أَبُو دَاوُد
Translation
Ibn ‘Umar said that the Prophet matted his hair with ghisl (A lotion made of marsh-mallows, or lotus leaves, or fuller’s earth, or potash with water). Abu Dawud transmitted it.