Weak
graded by Al-Albani
Mishkat al-Masabih 446
Narrator:Ā’ishah
وَعَنْ عَائِشَةَ قَالَتْ: كَانَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَغْسِلُ رَأْسَهُ بِالْخِطْمِيِّ وَهُوَ جُنُبٌ يَجْتَزِئُ بِذَلِكَ وَلَا يَصُبُّ عَلَيْهِ الْمَاءَ. رَوَاهُ أَبُو دَاوُد
She also said that the Prophet used to wash his head with marshmallow when sexually defiled, contenting himself with that and not pouring water over it. Abu Dawud transmitted it.
Reported by Abu Dawud (No. 256). Cited in Mishkat al-Masabih (No. 446).