Hadith on Bidah: You do not know what they innovated after you

Anas ibn Malik reported: The Prophet, peace and blessings be upon him, said, “Some of my companions will come to me at the fountain in the Hereafter, until I recognize them. They will be taken away from me, then I will say: My companions! It will be said: You do not know what they innovated after you.”

Source: Ṣaḥīḥ al-Bukhārī 6211, Ṣaḥīḥ Muslim 2304

Grade: Muttafaqun Alayhi (authenticity agreed upon) according to Al-Bukhari and Muslim

عَنْ أَنَسٍ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ لَيَرِدَنَّ عَلَىَّ نَاسٌ مِنْ أَصْحَابِي الْحَوْضَ حَتَّى عَرَفْتُهُمُ اخْتُلِجُوا دُونِي فَأَقُولُ أَصْحَابِي‏ فَيَقُولُ لاَ تَدْرِي مَا أَحْدَثُوا بَعْدَكَ

صحيح البخاري كتاب الرقاق باب في الحوض 6211

2304 صحيح مسلم كتاب الفضائل باب إثبات حوض نبينا صلى الله عليه وسلم وصفاته