Chapter on the Description of Ablution and Its Obligations
Tahdhīb al-Aḥkām|Volume 1|Book 1|Chapter 16
اَلْحُسَيْنُ بْنُ سَعِيدٍ عَنْ حَمَّادٍ عَنْ زُرَارَةَ قَالَ: قُلْتُ لَهُ أَ رَأَيْتَ مَا كَانَ تَحْتَ اَلشَّعْرِ قَالَ« كُلُّ مَا أَحَاطَ بِهِ اَلشَّعْرُ فَلَيْسَ لِلْعِبَادِ أَنْ يَغْسِلُوهُ وَ لاَ يَبْحَثُوا عَنْهُ وَ لَكِنْ يُجْرَى عَلَيْهِ اَلْمَاءُ».
Al-Husayn ibn Sa'id narrated from Hammad, from Zurara:
I said to Imam عليه السلام: "What about what lies beneath the hair during purification?" Imam عليه السلام said: "Whatever is covered by the hair, the people are not required to wash it or examine it. Instead, water should simply flow over it."
- Tahdhīb al-Aḥkām fī Sharḥ al-Muqniʿah, vol. 1, p. 388
- Ṣaḥīḥ al-Tahdhīb, p. 61