Musnad Ahmed: Hadith 3808

The Messenger of Allah (ﷺ) said: “There will emerge at the end of time people who are foolish and young. They will speak the best of people's speech and will recite the Qur'an with their tongues but it will not go past their collarbones. They will pass out of Islam as the arrow passes out of the prey. Whoever lives to see them, let him kill them for in killing them there is great reward with Allah, for the one who kills them.”