Congregational Prayer and Its Virtue
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 57
وَ رَوَى مُحَمَّدُ بْنُ عَلِيٍّ اَلْحَلَبِيُّ عَنْهُ عَلَيْهِ اَلسَّلاَمُ أَنَّهُ قَالَ: «لاَ تُصَلِّ خَلْفَ مَنْ يَشْهَدُ عَلَيْكَ بِالْكُفْرِ وَ لاَ خَلْفَ مَنْ شَهِدْتَ عَلَيْهِ بِالْكُفْرِ.
Muhammad ibn Ali Al-Halabi narrated from him عليه السلام that He said: "Do not pray behind someone who declares you to be an unbeliever (kafir), and do not pray behind someone whom you have declared to be an unbeliever."
- Ṣaḥīḥ al-Faqīh, p. 52