The Chapter on the Virtues of Prayer
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 31
وَقَالَ اَلصَّادِقُ عَلَيْهِ اَلسَّلاَمُ: «أَوَّلُ مَا يُحَاسَبُ بِهِ اَلْعَبْدُ عَلَى اَلصَّلاَةِ فَإِذَا قُبِلَتْ قُبِلَ مِنْهُ سَائِرُ عَمَلِهِ وَ إِذَا رُدَّتْ عَلَيْهِ رُدَّ عَلَيْهِ سَائِرُ عَمَلِهِ.
Imam Jafar ibn Muhammad Al-Sadiq عليه السلام said: "The first thing a servant will be held accountable for is prayer. If it is accepted, the rest of his deeds will be accepted; and if it is rejected, the rest of his deeds will be rejected."
- Ṣaḥīḥ al-Faqīh