Bulugh al-Maram 34
Narrated ‘Ali (rad)  regarding the description of the ablution of the Prophet (ﷺ):
He (the Prophet) wiped his head (with water) only once. [Reported by Abu Da’ud, An-Nasa’i, AtTirmidhi with a Sahih Sanad (authentic chain of narrators). At-Tirmidhi said, “It’s the most Hadith on this subject”].
وَعَنْ عَلِيٍّ ‏- رضى الله عنه ‏- ‏-فِي صِفَةِ وُضُوءِ اَلنَّبِيِّ صَلَّى اَللَّهُ عَلَيْهِ وَسَلَّمَ‏- قَالَ: { وَمَسَحَ بِرَأْسِهِ وَاحِدَةً.‏ }  أَخْرَجَهُ أَبُو دَاوُد َ  1‏ .‏‏1 ‏- صحيح.‏ رواه أبو داود (111)‏.‏