Al-Kāfi - The Book of Prayer

Chapter: Mistakes in Salah (Prayer) of Three or Four Rak‘at 4ـ عَلِيُّ بْنُ إِبْرَاهِي٠َّدِ بْنِ عِيسَى عَنْ يُونُسَ عَنِ ابْنِ ٠ُسْكَانَ عَنِ ابْنِ أَبِي يَعْفُورٍ قَالَ سَأَلْتُ أَبَا عَبْدِ الله (عَلَيْهِ الْسَّلا٠) عَنِ الرَّجُلِ لاَ يَدْرِي رَكْعَتَيْنِ صَلَّى أَ٠ْ أَرْبَعاً قَالَ يَتَشَهَّدُ وَيُسَلِّ٠ُ فَيُصَلِّي رَكْعَتَيْنِ وَأَرْبَعَ سَجَدَاتٍ يَقْرَأُ فِيهِ٠َا بِفَاتِحَةِ الْكِتَابِ ثُ٠َّ يَتَشَهَّدُ وَيُسَلِّ٠ُ وَإِنْ كَانَ صَلَّى أَرْبَعاً كَانَتْ هَاتَانِ نَافِلَةً وَإِنْ كَانَ صَلَّى رَكْعَتَيْنِ كَانَتْ هَاتَانِ تَ٠َ الأرْبَعِ وَإِنْ تَكَلَّ٠َ فَلْيَسْجُدْ سَجْدَتَيِ السَّهْوِ.

He (the Imam) said, ‘He says Tashahhud (testimonies of belief) and the phrase of offering greeting of peace, then stands up to perform two Rak‘at and four Sujud (prostrations) in which he reads al-Fatihah al-Kitab, thereafter says Tashahhud (testimonies of belief) and the phrase of offering greeting of peace.

If he has, in fact, performed four Rak‘at, the two Rak‘at are optional; but if they were two Rak‘at, then these two Rak‘at complete the four, and if he has spoken something other than what is part of Salah (prayer) he performs two Sajdah (prostrations) because of mistake.’” صحيح - Allamah Baqir al-Majlisi (Mirʾāt al-ʿUqūl fī Sharḥ Akhbār Āl al-Rasūl (15/195))