Sahih al-Bukhari 1294
Sahih al-Bukhari · Book 23: Funerals (Al-Janaa'iz) · He who tears off his clothes (when afflicted with a calamity) is not from us
Narrated `Abdullah:
حَدَّثَنَا أَبُو نُعَيْمٍ ، حَدَّثَنَا سُفْيَانُ ، حَدَّثَنَا زُبَيْدٌ الْيَامِيُّ ، عَنْ إِبْرَاهِيمَ ، عَنْ مَسْرُوقٍ ، عَنْ عَبْدِ اللَّهِ ـ رضى الله عنه ـ قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم " لَيْسَ مِنَّا مَنْ لَطَمَ الْخُدُودَ، وَشَقَّ الْجُيُوبَ، وَدَعَا بِدَعْوَى الْجَاهِلِيَّةِ " .
the Prophet (ﷺ) said, "He who slaps his cheeks, tears his clothes and follows the ways and traditions of the Days of Ignorance is not one of us."