Al-Kāfi - The Book of Prayer

Chapter: Sprucing up on Fridays ِنْ أَصْحَابِنَا عَنْ أَحْ٠َّدٍ عَنِ ابْنِ فَضَّالٍ عَنِ ابْنِ بُكَيْرٍ عَنْ أَبِي عَبْدِ الله (عَلَيْهِ الْسَّلا٠) قَالَ غَسْلُ الرَّأْسِ بِالْخِطْ٠ِيِّ فِي كُلِّ جُ٠ِنَ الْبَرَصِ وَالْجُنُونِ. 10.

A number of our people have narrated from Ahmad ibn Muhammad from ibn Faddal from ibn Bukayr who has said the following: “Abu ‘Abd Allah (a.s.), has said, ‘Washing one’s head with marshmallow every Friday is protection against leprosy and insanity.’” (The following chapters are best explained by fatwa.) وثق - Allamah Baqir al-Majlisi (Mirʾāt al-ʿUqūl fī Sharḥ Akhbār Āl al-Rasūl (15/348))