Any person who called his brother: "O unbeliever" (has in fact done an act by which this unbelief) would return to one of them. If it were so, as he asserted (then the unbelief of man was confirmed but if it was not true), then it returned to him (to the man who labeled it on his brother Muslim).
قَالَ رَسُولُ اللَّهِ ﷺ أَيُّمَا امْرِئٍ قَالَ لأَخِيهِ يَا كَافِرُ فَقَدْ بَاءَ بِهَا أَحَدُهُمَا إِنْ كَانَ كَمَا قَالَ وَإِلاَّ رَجَعَتْ عَلَيْهِ
The Messenger of Allah ﷺ said, "If anyone says to his brother O kāfir (disbeliever)! Then surely, one of them such."
أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ: «أَيُّمَا رَجُلٍ قَالَ لأَخِيهِ: يَا كَافِرُ، فَقَدْ بَاءَ بِهَا أَحَدُهُمَا۔»
Malik related to me from Abdullah ibn Dinar from Abdullah ibn Umar that the Messenger of Allah ﷺ said, "If a man says to his muslim brother, 'O kafir!' it is true about one of them."
أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ مَنْ قَالَ لأَخِيهِ يَا كَافِرُ فَقَدْ بَاءَ بِهَا أَحَدُهُمَا
[Machine] The Messenger of Allah ﷺ said: "Whoever says to his brother, 'O disbeliever,' one of them has indeed earned it."
قَالَ رَسُولُ اللهِ ﷺ مَنْ قَالَ لِأَخِيهِ يَا كَافِرُ فَقَدْ بَاءَ بِهَا أَحَدُهُمَا
Messenger of Allah ﷺ said, 'If anyone says to his brother, 'O misbeliever! Then surely, one of them such." (Using translation from Bukhārī 6104)
قَالَ رَسُولُ اللهِ ﷺ أَيُّمَا رَجُلٍ قَالَ لِأَخِيهِ يَا كَافِرُ فَقَدْ بَاءَ بِهَا أَحَدُهُمَا
[Machine] The Prophet ﷺ said, "If any of you says to his brother, 'O disbeliever,' then it will surely apply to one of them."
عَنِ النَّبِيِّ ﷺ قَالَ إِذَا أَحَدُكُمْ قَالَ لِأَخِيهِ يَا كَافِرُ فَقَدْ بَاءَ بِهَا أَحَدُهُمَا
[Machine] The Messenger of Allah ﷺ said, "Whoever says to his brother 'O disbeliever,' then surely one of them has earned it."
قَالَ رَسُولُ اللهِ ﷺ أَيُّمَا امْرِئٍ قَالَ لِأَخِيهِ يَا كَافِرُ فَقَدْ بَاءَ بِهَا أَحَدُهُمَا
[Machine] From the Prophet ﷺ that he said, "When a man says to another man, 'O disbeliever,' then one of them will bear the consequences of what he said, if it is as he described. Otherwise, it will return upon the other."
عَنِ النَّبِيِّ ﷺ أَنَّهُ قَالَ إِذَا قَالَ الرَّجُلُ لِلرَّجُلِ يَا كَافِرُ فَقَدْ بَاءَ بِهِ أَحَدُهُمَا إِنْ كَانَ كَمَا قَالَ وَإِلَّا رَجَعَتْ عَلَى الْآخَرِ
Messenger of Allah ﷺ said, 'If anyone says to his brother, 'O misbeliever! Then surely, one of them such." (Using translation from Bukhārī 6104)
أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ «أَيُّمَا رَجُلٌ قَالَ لِأَخِيهِ كَافِرٌ فَقَدْ بَاءَ بِهِ أَحَدُهُمَا»
Any person who called his brother: "O unbeliever" (has in fact done an act by which this unbelief) would return to one of them. If it were so, as he asserted (then the unbelief of man was confirmed but if it was not true), then it returned to him (to the man who labeled it on his brother Muslim). (Using translation from Muslim 60b)
قَالَ رَسُولُ اللَّهِ ﷺ «أَيُّمَا امْرِئٍ قَالَ لِأَخِيهِ كَافِرٌ فَقَدْ بَاءَ بِهِ أَحَدُهُمَا إِنْ كَانَ كَمَا قَالَ وَإِلَّا رَجَعَتْ عَلَيْهِ»
"أيُّمَا امْرِئ قَال لأخيه "كَافِرٌ" فَقَدْ بَاءَ بها أحَدُهُمَا إِنْ كَانَ كمَا قَال، وَإلا رَجَعتْ عَلَيهِ ".
"إذا قال الرَّجلُ لأخيه: يا كافرُ فقدْ باءَ بِهِ أحدُهُما: إنْ كانَ الذِي قيل له كافرًا (فهُوَ كافِرٌ) وإلا رجعَ إلى مَنْ قالَ".