Bulugh al-Maram 1 The Book of Purification كتاب الطهارة 39

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).

Narrated ‘Ali (rad) regarding the description of the ablution of the Prophet (صلى الله عليه وسلم): 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”].