‘Imran ibn Husayn reported: The Messenger of Allah, peace and blessings be upon him, said, “If a man declares his brother to be an unbeliever, it is as if he has killed him. Cursing a believer is like killing him.”
Source: Musnad al-Bazzār 3158
Grade: Sahih (authentic) according to Al-Albani
عَنْ عِمْرَانَ بْنِ حُصَيْنٍ قَالَ قَالَ رَسُولُ اللَّهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ إِذَا قَالَ الرَّجُلُ لِأَخِيهِ يَا كَافِرُ فَهُوَ كَقَتْلِهِ وَلَعْنُ الْمُؤْمِنِ كَقَتْلِهِ
3158 مسند البزار
710 المحدث الألباني خلاصة حكم المحدث صحيح في صحيح الجامع
