وَ رَوَى اَلْعَلاَءُ عَنْ مُحَمَّدِ بْنِ مُسْلِمٍ عَنْ أَبِي عَبْدِ اَللَّهِ عَلَيْهِ اَلسَّلاَمُ قَالَ: سَأَلْتُهُ عَنْ رَجُلٍ صَلَّى اَلظُّهْرَ خَمْساً فَقَالَ «إِنْ كَانَ لاَ يَدْرِي جَلَسَ فِي اَلرَّابِعَةِ أَمْ لَمْ يَجْلِسْ فَلْيَجْعَلْ أَرْبَعَ رَكَعَاتٍ مِنْهَا اَلظُّهْرَ وَ يَجْلِسُ وَ يَتَشَهَّدُ ثُمَّ يُصَلِّي وَ هُوَ جَالِسٌ رَكْعَتَيْنِ وَ أَرْبَعَ سَجَدَاتٍ فَيُضِيفُهُمَا إِلَى اَلْخَامِسَةِ فَتَكُونُ نَافِلَةً.
Al-Ala reported from Muhammad ibn Muslim from Imam Jafar ibn Muhammad Al-Sadiq (a.s) who said: "I asked him about a man who prayed Dhuhr five rak'ahs. He said: 'If he does not know whether he sat in the fourth rak'ah or not, let him treat it as four rak'ahs for the Dhuhr prayer, then he should sit, perform the tashahhud, and then pray two rak'ahs while sitting and perform four sajdahs. He should then add these to the fifth rak'ah, and it will be considered a nafl (voluntary) prayer.'"