(1) بَابُ مَا جَاءَ فِي قَوْلِ اللَّهِ تَعَالَى: {وَاتَّقُوا فِتْنَةً لاَ تُصِيبَنَّ الَّذِينَ ظَلَمُوا مِنْكُمْ خَاصَّةً}
Abu Sa`id Al-Khudri added that the Prophet (ﷺ) further said:
"I will say those people are from me. It will be said, 'You do not know what changes and new things they did after you.' Then I will say, 'Far removed (from mercy), far removed (from mercy), those who changed (the religion) after me!"
Reference: Sahih al-Bukhari 7051
In-book reference: Book 92, Hadith 4
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 9, Book 88, Hadith 174