What Can and Cannot Be Used for Prostration
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 41
وَ رَوَى عَمَّارٌ اَلسَّابَاطِيُّ عَنْ أَبِي عَبْدِ اَللَّهِ عَلَيْهِ اَلسَّلاَمُ أَنَّهُ قَالَ: «مَا بَيْنَ قُصَاصِ اَلشَّعْرِ إِلَى طَرَفِ اَلْأَنْفِ مَسْجِدٌ فَمَا أَصَابَ اَلْأَرْضَ مِنْهُ فَقَدْ أَجْزَأَكَ.
Ammar al-Sabati narrate from Imam Jafar ibn Muhammad Al-Sadiq عليه السلام that He said: "The area between the hairline and the tip of the nose is considered a place of prostration (masjid), so whatever part of it touches the ground suffices."
- Ṣaḥīḥ al-Faqīh