In the Name of Allah, the Gracious, the Merciful
Imam al-Mundhiri recorded the chapter in his book Inspiring Hope and Inciting Fear:
الترهيب من قوله لمسلم يا كافر
Discouragement from declaring a Muslim to be an unbeliever.
Source: al-Targhīb wal-Tarhīb 3/463
Ibn Umar reported: The Messenger of Allah, peace and blessings be upon him, said:
أَيُّمَا امْرِئٍ قَالَ لِأَخِيهِ يَا كَافِرُ فَقَدْ بَاءَ بِهَا أَحَدُهُمَا إِنْ كَانَ كَمَا قَالَ وَإِلَّا رَجَعَتْ عَلَيْهِ
When a man calls his brother an unbeliever, it turns against at least one of them. Either the accused is as he claimed, or else the charge will turn against him.
Source: Ṣaḥīḥ al-Bukhārī 6104, Grade: Muttafaqun Alayhi
Abu Dharr reported: The Prophet, peace and blessings be upon him, said:
لَا يَرْمِي رَجُلٌ رَجُلًا بِالْفُسُوقِ وَلَا يَرْمِيهِ بِالْكُفْرِ إِلَّا ارْتَدَّتْ عَلَيْهِ إِنْ لَمْ يَكُنْ صَاحِبُهُ كَذَلِكَ
A man does not accuse another man of wickedness or unbelief except that it will be turned against him, if his companion is innocent.
Source: Ṣaḥīḥ al-Bukhārī 6045, Grade: Sahih
Abu Huraira reported: The Messenger of Allah, peace and blessings be upon him, said:
إِذَا قَالَ الرَّجُلُ لِأَخِيهِ يَا كَافِرُ فَقَدْ بَاءَ بِهِ أَحَدُهُمَا
When a man accuses his brother of being an unbeliever, then it will be turned against at least one of them.
Source: Ṣaḥīḥ al-Bukhārī 6103, Grade: Sahih
Thabit ibn al-Dahhak reported: The Prophet, peace and blessings be upon him, said:
لَعْنُ الْمُؤْمِنِ كَقَتْلِهِ وَمَنْ رَمَى مُؤْمِنًا بِكُفْرٍ فَهُوَ كَقَتْلِهِ
Cursing a believer is like killing him, and accusing a believer of unbelief is like killing him.
Source: Ṣaḥīḥ al-Bukhārī 6105, Grade: Muttafaqun Alayhi
‘Imran ibn Husayn reported: The Messenger of Allah, peace and blessings be upon him, said:
إِذَا قَالَ الرَّجُلُ لِأَخِيهِ يَا كَافِرُ فَهُوَ كَقَتْلِهِ وَلَعْنُ الْمُؤْمِنِ كَقَتْلِهِ
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
Success comes from Allah, and Allah knows best.
