The Rules of Forgetfulness (Sahw) in Prayer
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 50
وَ رَوَى عَبْدُ اَللَّهِ بْنُ سِنَانٍ عَنْ أَبِي عَبْدِ اَللَّهِ عَلَيْهِ اَلسَّلاَمُ أَنَّهُ قَالَ: «إِذَا نَسِيتَ شَيْئاً مِنَ اَلصَّلاَةِ رُكُوعاً أَوْ سُجُوداً أَوْ تَكْبِيراً ثُمَّ ذَكَرْتَ فَاقْضِ اَلَّذِي فَاتَكَ سَهْواً.
Abdullah ibn Sinan narrated from Imam Jafar ibn Muhammad Al-Sadiq عليه السلام that He said: "If you forget something in the prayer, whether it is bowing, prostration, or takbir, and then remember it, make up for what you missed due to forgetfulness”.
- Ṣaḥīḥ al-Faqīh