Description of the Prayer from Its Beginning to Its End
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 46
وَقَالَ اَلرِّضَا عَلَيْهِ اَلسَّلاَمُ: «إِنَّمَا جُعِلَ اَلْقِرَاءَةُ فِي اَلرَّكْعَتَيْنِ اَلْأَوَّلَتَيْنِ وَ اَلتَّسْبِيحُ فِي اَلْأَخِيرَتَيْنِ لِلْفَرْقِ بَيْنَ مَا فَرَضَهُ اَللَّهُ عَزَّ وَ جَلَّ مِنْ عِنْدِهِ وَ بَيْنَ مَا فَرَضَهُ اَللَّهُ تَعَالَى مِنْ عِنْدِ رَسُولِ اَللَّهِ صَلَّى اَللَّهُ عَلَيْهِ وَ آلِهِ.
Imam al-Ridha عليه السلام said: "The reason why recitation is required in the first two rak‘ahs and glorification (tasbih) in the last two rak‘ahs of the prayer is to distinguish between what Allah سبحانه وتعالى, the Exalted, has ordained from Himself and what He has commanded through His Messenger”.
- Ṣaḥīḥ al-Faqīh