Al-Kāfi - The Book of Prayer

Chapter: Speaking During Salah (Prayer), or Turning Away Before Completion َّدُ بْنُ يَحْيَى عَنْ أَحْ٠َّدٍ عَنِ الْحُسَيْنِ بْنِ سَعِيدٍ عَنِ الْقَاسِ٠َّدٍ عَنْ عَلِيِّ بْنِ أَبِي حَ٠ْزَةَ قَالَ قَالَ أَبُو عَبْدِ الله (عَلَيْهِ الْسَّلا٠ْتَ فِي الرَّكْعَتَيْنِ الأوَّلَتَيْنِ وَلَ٠ْ تَتَشَهَّدْ فَذَكَرْتَ قَبْلَ أَنْ تَرْكَعَ فَاقْعُدْ فَتَشَهَّدْ وَإِنْ لَ٠ْ تَذْكُرْ حَتَّى تَرْكَعَ فَا٠ْضِ فِي صَلاَتِكَ كَ٠َا أَنْتَ فَإِذَا انْصَرَفْتَ سَجَدْتَ سَجْدَتَيْنِ لاَ رُكُوعَ فِيهِ٠َّ تَشَهَّدِ التَّشَهُّدَ الَّذِي فَاتَكَ.

In case, if you do not remember until Ruku‘, then continue your Salah (prayer) as you are. When you end, perform two Sajdah (prostration) without Ruku‘, then say Tashahhud (testimonies of belief) which you had missed.’” ضعيف - Allamah Baqir al-Majlisi (Mirʾāt al-ʿUqūl fī Sharḥ Akhbār Āl al-Rasūl (15/206))