Authentic
graded by Al-Albani
Mishkat al-Masabih 2684
Narrator:Abu Ayyūb al-Ansāri
وَعَن أَبِي أَيُّوبَ: أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ كَانَ يَغْسِلُ رَأْسَهُ وَهُوَ مُحْرِمٌ
Abu Ayyub said that the Prophet used to wash his head when he was in the sacred state. Bukhari and Muslim.
Cited in Mishkat al-Masabih (No. 2684).