The Prayer of Seeking Guidance (Istikhara)
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 84
وَ سَأَلَ مُحَمَّدُ بْنُ خَالِدٍ اَلْقَسْرِيُّ أَبَا عَبْدِ اَللَّهِ عَلَيْهِ اَلسَّلاَمُ عَنِ اَلاِسْتِخَارَةِ فَقَالَ «اِسْتَخِرِ اَللَّهَ فِي آخِرِ رَكْعَةٍ مِنْ صَلاَةِ اَللَّيْلِ وَ أَنْتَ سَاجِدٌ مِائَةَ مَرَّةٍ وَ مَرَّةً» قَالَ كَيْفَ أَقُولُ قَالَ «تَقُولُ أَسْتَخِيرُ اَللَّهَ بِرَحْمَتِهِ أَسْتَخِيرُ اَللَّهَ بِرَحْمَتِهِ.
Muhammad ibn Khalid al-Qasri asked Imam Jafar ibn Muhammad Al-Sadiq عليه السلام about seeking divine guidance (istikhara). Imam عليه السلام said: "Seek guidance from Allah سبحانه وتعالى in the last unit (rak'ah) of the night prayer while you are in prostration, repeating it one hundred and one times." Muhammad asked: "How should I say it?" Imam عليه السلام said: "You should say, Astakheeru Allāha bi-raḥmatihi, astakheeru Allāha bi-raḥmatihi. 'I seek guidance from Allah سبحانه وتعالى by His mercy, I seek guidance from Allah سبحانه وتعالى by His mercy.'"
- Ṣaḥīḥ al-Faqīh