The Rules of Forgetfulness (Sahw) in Prayer
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 50
وَ رَوَى اَلْحُسَيْنُ بْنُ حَمَّادٍ عَنْ أَبِي عَبْدِ اَللَّهِ عَلَيْهِ اَلسَّلاَمُ: أَنَّهُ قَالَ لَهُ أَسْهُو عَنِ اَلْقِرَاءَةِ فِي اَلرَّكْعَةِ اَلْأُولَى قَالَ «اِقْرَأْ فِي اَلثَّانِيَةِ» قَالَ قُلْتُ أَسْهُو فِي اَلثَّانِيَةِ قَالَ «اِقْرَأْ فِي اَلثَّالِثَةِ» قَالَ قُلْتُ أَسْهُو فِي صَلاَتِي كُلِّهَا فَقَالَ «إِذَا حَفِظْتَ اَلرُّكُوعَ وَ اَلسُّجُودَ فَقَدْ تَمَّتْ صَلاَتُكَ.
Hussain ibn Hammad narrated from Imam Jafar ibn Muhammad Al-Sadiq عليه السلام that a man said to him: "I forget the recitation in the first rak'ah." Imam عليه السلام said: "Recite in the second." The man then said: "I forget in the second rak'ah as well." Imam عليه السلام said: "Recite in the third." The man said: "I forget throughout my entire prayer." Imam عليه السلام said: "If you have remembered the ruku' (bowing) and Sujood (prostration), then your prayer is complete."
- Ṣaḥīḥ al-Faqīh