The Prayer of Fear, Pursuit, Encounter, and Competition
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 63
وَ رَوَى عُبَيْدُ اَللَّهِ بْنُ عَلِيٍّ اَلْحَلَبِيُّ عَنْ أَبِي عَبْدِ اَللَّهِ عَلَيْهِ اَلسَّلاَمُ قَالَ: «صَلاَةُ اَلزَّحْفِ عَلَى اَلظَّهْرِ إِيمَاءٌ بِرَأْسِكَ وَ تَكْبِيرٌ وَ اَلْمُسَايَفَةِ تَكْبِيرٌ بِغَيْرِ إِيمَاءٍ وَ اَلْمُطَارَدَةِ إِيمَاءٌ يُصَلِّي كُلُّ رَجُلٍ عَلَى حِيَالِهِ.
Ubaydullah ibn Ali Al-Halabi reported from Imam Jafar ibn Muhammad Al-Sadiq عليه السلام who said: "The prayer during advancing combat (al-zahf) is performed on one's back with gestures of the head and the takbir (proclamation of 'Allahu Akbar'). During close fighting (al-musayafa), it involves takbir without gestures. During pursuit (al-mutarada), it is performed with gestures, and each person prays individually as per their situation."
- Ṣaḥīḥ al-Faqīh