Congregational Prayer and Its Virtue
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 57
وَ رَوَى عَمَّارٌ اَلسَّابَاطِيُّ عَنْ أَبِي عَبْدِ اَللَّهِ عَلَيْهِ اَلسَّلاَمُ قَالَ: سَأَلْتُهُ عَنِ اَلرَّجُلِ يَنْسَى وَ هُوَ خَلْفَ اَلْإِمَامِ أَنْ يُسَبِّحَ فِي اَلسُّجُودِ أَوْ فِي اَلرُّكُوعِ أَوْ يَنْسَى أَنْ يَقُولَ بَيْنَ اَلسَّجْدَتَيْنِ شَيْئاً قَالَ «لَيْسَ عَلَيْهِ شَيْءٌ.
Ammar al-Sabati narrated from Imam Jafar ibn Muhammad Al-Sadiq عليه السلام who said: "I asked him about a man who, while praying behind an Imam, forgets to say the tasbih (glorification) during Sujood (prostration) or ruku' (bowing) or forgets to say something between the two prostrations." Imam عليه السلام said: "There is no obligation upon him (no penalty)."
- Ṣaḥīḥ al-Faqīh