Abu Sa'id Al-Khudri related that Abu Bakr came to the Messenger of Allah (SAW) and said: Oh Messenger of Allah, indeed I was passing through such-and-such valley, and there was a humbly submissive, well-groomed man there praying. The Prophet (SAW) said to him: Go to him and kill him. And Abu Bakr went to him, but when he saw him in that position, he really didn't want to kill him. So he returned to the Messenger of Allah (SAW). Then the Prophet (SAW) said to 'Umar: Go kill him. So 'Umar went, and saw him in the same position that Abu Bakr had seen him, and he really didn't want to kill him either. So he returned, and said: Oh Messenger of Allah, indeed I saw him praying humbly and submissive, and I really didn't want to kill him. Then He said: Oh 'Ali! Go kill him. And 'Ali went, but could not find him. So 'Ali returned and said: Oh Messenger of Allah, indeed he couldn't find him. And the Messenger of Allah (SAW) said: Truly this man and his companions recite the Qur'an without it going past their throats, they pass through and out of the deen like an arrow passes through and out of its target, and until the arrow returns to its bowstring they will not return to the deen; so kill them; they are the worst of creatures.