The Rules of Forgetfulness (Sahw) in Prayer
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 50
وَ رَوَى زُرَارَةُ عَنْ أَبِي جَعْفَرٍ عَلَيْهِ اَلسَّلاَمُ أَنَّهُ قَالَ: «لاَ تُعَادُ اَلصَّلاَةُ إِلاَّ مِنْ خَمْسَةٍ اَلطَّهُورِ وَ اَلْوَقْتِ وَ اَلْقِبْلَةِ وَ اَلرُّكُوعِ وَ اَلسُّجُودِ» ثُمَّ قَالَ «اَلْقِرَاءَةُ سُنَّةٌ وَ اَلتَّشَهُّدُ سُنَّةٌ وَ لاَ تَنْقُضُ اَلسُّنَّةُ اَلْفَرِيضَةَ.
Zurarah narrated from Imam Muhammad ibn Ali Al-Baqir عليه السلام that He said: "The prayer is only to be repeated in five cases : purification (tahur), time (waqt), the direction of the Qiblah, the bowing (ruku'), and prostration (Sujood)." He then said: "Recitation (qira'ah) is a Sunnah, and the testimony (tashahhud) is a Sunnah, and the Sunnah does not invalidate the obligatory act (fardh)”.
- Ṣaḥīḥ al-Faqīh, p. 46