The Chapter on the Virtues of Prayer
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 31
وَقَالَ اَلصَّادِقُ عَلَيْهِ اَلسَّلاَمُ: «أَحَبُّ اَلْأَعْمَالِ إِلَى اَللَّهِ عَزَّ وَ جَلَّ اَلصَّلاَةُ وَ هِيَ آخِرُ وَصَايَا اَلْأَنْبِيَاءِ عَلَيْهِمُ اَلسَّلاَمُ فَمَا أَحْسَنَ مِنَ اَلرَّجُلِ أَنْ يَغْتَسِلَ أَوْ يَتَوَضَّأَ فَيُسْبِغَ اَلْوُضُوءَ ثُمَّ يَتَنَحَّى حَيْثُ لاَ يَرَاهُ أَنِيسٌ فَيُشْرِفَ اَللَّهُ عَزَّ وَ جَلَّ عَلَيْهِ وَ هُوَ رَاكِعٌ أَوْ سَاجِدٌ إِنَّ اَلْعَبْدَ إِذَا سَجَدَ فَأَطَالَ اَلسُّجُودَ نَادَى إِبْلِيسُ يَا وَيْلاَهْ أَطَاعُوهُ وَ عَصَيْتُ وَ سَجَدُوا وَ أَبَيْتُ.
Imam Jafar ibn Muhammad Al-Sadiq عليه السلام said: "The most beloved of deeds to Allah سبحانه وتعالى, the Mighty and Majestic, is prayer. It is the final counsel of the prophets عليه السلام. How beautiful it is for a person to perform ghusl (ritual bathing) or ablution (wudu'), perfecting it thoroughly, then to go to a place where no one can see him, and to humble himself before Allah سبحانه وتعالى, the Mighty and Majestic, in bowing (ruku') or prostration (Sujood). When a servant prostrates and prolongs his prostration, Iblis (Satan) cries out, 'Woe to me! They obeyed Him, while I disobeyed Him, and they prostrated while I refused.'".
- Ṣaḥīḥ al-Faqīh