What Can and Cannot Be Used for Prostration
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 41
وَ رُوِيَ عَنِ اَلصَّادِقِ عَلَيْهِ اَلسَّلاَمُ أَنَّهُ قَالَ: «إِنَّمَا يُكْرَهُ ذَلِكَ خَشْيَةَ أَنْ يُؤْذَى مَنْ إِلَى جَانِبِهِ.
It was narrated from Imam Jafar ibn Muhammad Al-Sadiq عليه السلام that He said: "It is disliked (makruh) because it may cause harm to the person next to him."
- Ṣaḥīḥ al-Faqīh