Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates: I heard the Prophet (peace and blessings be upon him) say: "Some people will emerge from my Ummah whose deeds will be evil. They will recite the Qur'an, but it will not go beyond their throats." Yazid says: To my knowledge the narration also contains these words: "One of you will consider his own deeds insignificant compared with their deeds. They will kill the people of Islam. When they rebel, kill them; then if they emerge, kill them; then if they emerge, kill them. For glad tidings are for the one who kills them, and glad tidings are also for the one whom they kill. Whenever a group of them emerges, Allah Almighty will have it destroyed." The Prophet (peace and blessings be upon him) repeated this twenty times or more, while I was listening.
Ahmad recorded it. Its chain contains the narrator Abu Janab, who is a mudallis.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب قتال أهل البغي / 10411