The Rules of Forgetfulness (Sahw) in Prayer
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 50
وَ سَأَلَهُ عَمَّارٌ اَلسَّابَاطِيُّ: عَنْ سَجْدَتَيِ اَلسَّهْوِ هَلْ فِيهِمَا تَكْبِيرٌ أَوْ تَسْبِيحٌ فَقَالَ «لاَ إِنَّمَا هُمَا سَجْدَتَانِ فَقَطْ فَإِنْ كَانَ اَلَّذِي سَهَا هُوَ اَلْإِمَامَ كَبَّرَ إِذَا سَجَدَ وَ إِذَا رَفَعَ رَأْسَهُ لِيَعْلَمَ مَنْ خَلْفَهُ أَنَّهُ قَدْ سَهَا فَلَيْسَ عَلَيْهِ أَنْ يُسَبِّحَ فِيهِمَا وَ لاَ فِيهِمَا تَشَهُّدٌ بَعْدَ اَلسَّجْدَتَيْنِ.
Ammar al-Sabati asked him about the two prostrations of forgetfulness (Sajdat al-Sahw), and whether there is any Takbir (saying "Allahu Akbar") or Tasbih (glorification) in them. He (Imam Ja'far Al-Sadiq) replied: "No, they are simply two prostrations. If the one who forgot is the Imam, then he should say Takbir when he prostrates and when he raises his head, so that those behind him know that he has made a mistake. There is no need for him to say Tasbih in them, and there is no need for any Tashahhud (testification) after the two prostrations."
- Ṣaḥīḥ al-Faqīh