كتاب الأمور المنهي عنها
18
The Book of the Prohibited actions
Ibn Mas'ud (May Allah be pleased with him) said:
The Messenger of Allah (ﷺ) said, "He who (on befalling a calamity) slaps his cheeks, tears his clothes and follows the ways and traditions of the Days of Ignorance is none of us."

[Al-Bukhari and Muslim].

وعن ابن مسعود رضي الله عنه قال‏:‏ قال رسول الله صلى الله عليه وسلم ‏:‏‏ "‏ليس منا من ضرب الخدود، وشق الجيوب، ودعا بدعوى الجاهليه‏"‏ ‏(‏‏(‏متفق عليه‏)‏‏)‏‏.‏
Sunnah.com reference : Book 18, Hadith 148
Arabic/English book reference : Book 18, Hadith 1658