It was narrated from Ibn 'Umar that:
The Messenger of Allah said: "There will emerge people who will recite the Qur'an but it will not go any deeper than their collarbones. Whenever a group of them appears, they should be cut off (i.e. killed)." Ibn 'Umar said: "I heard the Messenger of Allah say: 'Whenever a group of them appears, they should be killed' - (he said it) more than twenty times- 'until Dajjal emerges among them.'"
English reference: Vol. 1, Book 1, Hadith 174
Arabic reference: Book 1, Hadith 179