(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. (ID)
Reference (ID): Sahih Muslim 60 a (ID)
In-book reference (ID): Book 1, Hadith 121 (ID)
USC-MSA web (English) reference(deprecated numbering scheme): Book 1, Hadith 116 (ID)