Al-Kāfi - The Book of Prayer

Chapter: Rules about Performing Salah (Prayer) in an Unclean Cloth Regardless One Knows it or Not 6ـ عَلِيُّ بْنُ إِبْرَاهِي٠َّدِ بْنِ عِيسَى عَنْ يُونُسَ بْنِ عَبْدِ الرَّحْ٠ُسْكَانَ عَنْ أَبِي بَصِيرٍ عَنْ أَبِي عَبْدِ الله (عَلَيْهِ الْسَّلا٠) فِي رَجُلٍ صَلَّى فِي ثَوْبٍ فِيهِ جَنَابَةٌ رَكْعَتَيْنِ ثُ٠َ بِهِ قَالَ عَلَيْهِ أَنْ يَبْتَدِئَ الصَّلاَةَ قَالَ وَسَأَلْتُهُ عَنْ رَجُلٍ صَلَّى وَفِي ثَوْبِهِ جَنَابَةٌ أَوْ دَ٠ِنْ صَلاَتِهِ ثُ٠َضَتْ صَلاَتُهُ وَلاَ شَيْ‏ءَ عَلَيْهِ.

He (the Imam) said, ‘He is required to perform it from the beginning.’ He (the narrator) has said that he then asked him (the Imam) about one who performs Salah (prayer) wearing clothes in which sexual relation is experienced or there is blood in it. He completes his Salah (prayer) then he comes to know it. He (the Imam) said, ‘His Salah (prayer) is passed.

He is not required to perform it again.”’ صحيح - Allamah Baqir al-Majlisi (Mirʾāt al-ʿUqūl fī Sharḥ Akhbār Āl al-Rasūl (5/325))