Congregational Prayer and Its Virtue
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 57
وَ رَوَى جَمِيلُ بْنُ دَرَّاجٍ عَنْهُ عَلَيْهِ اَلسَّلاَمُ: فِي رَجُلٍ أَمَّ قَوْماً عَلَى غَيْرِ وُضُوءٍ فَانْصَرَفَ وَ قَدَّمَ رَجُلاً وَ لَمْ يَدْرِ اَلْمُقَدَّمُ مَا صَلَّى اَلْإِمَامُ قَبْلَهُ قَالَ «يُذَكِّرُهُ مَنْ خَلْفَهُ.
Jamil ibn Darraj narrated from Imam عليه السلام regarding a man who led a congregation in prayer without wudu' (ritual purity), then left and appointed another man to lead, but the new leader did not know what the previous Imam had prayed. Imam عليه السلام said: "Those behind him should remind him."
- Ṣaḥīḥ al-Faqīh, p. 58