وَعَنْ عَلِيٍّ رضى الله عنه (فِي صِفَةِ وُضُوءِ
اَلنَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ) قَالَ: «وَمَسَحَ بِرَأْسِهِ وَاحِدَةً»
He (the Prophet (sallallahu alayhi wa sallam)) wiped his head (with water) only once.
Bulugh al-Maram 39, Book 1, The Book of Purification, Hadith 39. 1 min read