The Chapter of the Qibla
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 43
وَقَالَ أَبُو جَعْفَرٍ عَلَيْهِ اَلسَّلاَمُ: «لاَ يَبْزُقَنَّ أَحَدُكُمْ فِي اَلصَّلاَةِ قِبَلَ وَجْهِهِ وَ لاَ عَنْ يَمِينِهِ وَ لْيَبْزُقْ عَنْ يَسَارِهِ وَ تَحْتِ قَدَمِهِ اَلْيُسْرَى.
Imam Muhammad ibn Ali Al-Baqir عليه السلام said: "None of you should spit in front of themselves or to their right while praying. Instead, they should spit to their left or beneath their left foot."
- Ṣaḥīḥ al-Faqīh