What Can and Cannot Be Used for Prostration
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 41
وَ رَوَى حَمَّادُ بْنُ عُثْمَانَ عَنْ أَبِي عَبْدِ اَللَّهِ عَلَيْهِ اَلسَّلاَمُ أَنَّهُ قَالَ: «اَلسُّجُودُ عَلَى مَا أَنْبَتَتِ اَلْأَرْضُ إِلاَّ مَا أُكِلَ أَوْ لُبِسَ.
Hamad ibn Uthman narrated from Imam Jafar ibn Muhammad Al-Sadiq عليه السلام that He said: "Prostration is to be done on what the earth produces, except for that which is eaten or worn."
- Ṣaḥīḥ al-Faqīh, p. 41