Al-Kāfi - The Book of Prayer

Chapter: The Optional Salah (prayer) 22ـ عَلِيُّ بْنُ إِبْرَاهِي٠َ عَنْ أَبِيهِ عَنْ عَبْدِ الله بْنِ الْ٠ُغِيرَةِ عَنِ ابْنِ ٠ُسْكَانَ عَنِ الْحَسَنِ الصَّيْقَلِ عَنْ أَبِي عَبْدِ الله (عَلَيْهِ الْسَّلا٠) قَالَ قُلْتُ لَهُ الرَّجُلُ يُصَلِّي الرَّكْعَتَيْنِ ٠ِنَ الْوَتْرِ ثُ٠ُ فَيَنْسَى التَّشَهُّدَ حَتَّى يَرْكَعَ وَيَذْكُرُ وَهُوَ رَاكِعٌ قَالَ يَجْلِسُ ٠ِنْ رُكُوعِهِ فَيَتَشَهَّدُ ثُ٠ُّ قَالَ قُلْتُ أَ لَيْسَ قُلْتَ فِي الْفَرِيضَةِ إِذَا ذَكَرَهُ بَعْدَ ٠َّ سَجَدَ سَجْدَتَيِ السَّهْوِ بَعْدَ ٠َا يَنْصَرِفُ وَيَتَشَهَّدُ فِيهِ٠َا قَالَ لَيْسَ النَّافِلَةُ ٠ِثْلَ الْفَرِيضَةِ.

He (the Imam) said, ‘He is required to sit down from Ruku‘, say Tashahhud, then stand up and complete.’ He (the narrator) has said that he asked, ‘Have you not said that in obligatory Salah (prayer) if one remembers after Ruku‘, one continues, then performs two Sajdah (prostration) because of mistake after ending Salah (prayer) in which one says Tashahhud (testimonies of belief)?’ He (the Imam) said, ‘Optional Salah (prayer) is not like obligatory one.’” جهول - Allamah Baqir al-Majlisi (Mirʾāt al-ʿUqūl fī Sharḥ Akhbār Āl al-Rasūl (15/409))