(26) باب بَيَانِ حَالِ إِيمَانِ مَنْ قَالَ لأَخِيهِ الْمُسْلِمِ يَا كَافِرُ
It is reported on the authority of Ibn 'Umar that the Apostle (may peace and blessings be upon him) observed:
When a man calls his brother an unbeliever, it returns (at least) to one of them. (RU)
Reference (RU): Sahih Muslim 60 a (RU)
In-book reference (RU): Book 1, Hadith 121 (RU)
USC-MSA web (English) reference(deprecated numbering scheme): Book 1, Hadith 116 (RU)