What Can and Cannot Be Used for Prostration
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 41
وَقَالَ عَلَيْهِ اَلسَّلاَمُ: «اَلسُّجُودُ عَلَى طِينِ قَبْرِ اَلْحُسَيْنِ عَلَيْهِ اَلسَّلاَمُ يُنَوِّرُ إِلَى اَلْأَرْضِ اَلسَّابِعَةِ.
Imam عليه السلام said: "Prostrating on the clay from the grave of Imam Hussain ibn Ali عليه السلام illuminates to the seventh layer of the earth."
- Ṣaḥīḥ al-Faqīh