صحيح مسلم

It is narrated by Safwan b. Muhriz that Jundab b. 'Abdullah al-Bajali during the stormy days of Ibn Zubair sent a message to 'As'as b. Salama: Gather some men of your family so that I should talk to them. He ('As'as) sent a messenger to them (to the members of his family). When they had assembled, Jundab came there with a yellow hooded cloak on him, He said: Talk what you were busy in talking. The talk went on by turns, till there came his (Jundab's) turn. He took off the hooded cloak from his head and said: I have come to you with no other intention but to narrate to you a hadith of your Apostle: Verily the Messenger of Allah (ﷺ) sent a squad of the Muslims to a tribe of the polytheists. Both the armies confronted one another. There was a man among the army of polytheists who (was so dashing that), whenever he intended to kill a man from among the Muslims, he killed him. Amongst the Muslims too was a man looking forward to (an opportunity of) his (the polytheist's) unmindfulness. He (the narrator) said: We talked that he was Usama b, Zaid. When he raised his sword, he (the soldier of the polytheists) uttered:" There is no god but Allah," but he (Usama b. Zaid) killed him. When the messenger of the glad tidings came to the Apostle (ﷺ) he asked him (about the events of the battle) and he informed him about the man (Usama) and what he had done He (the Prophet (ﷺ) of Allah) called for him and asked him why he had killed him. He (Usama) said: Messenger of Allah, he struck the Muslims and killed such and such of them. And he even named some of them. (He continued): I attacked him and when he saw the sword he said: There is no god but Allah. The Messenger of Allah (ﷺ) said: Did you kill him? He (Usama) replied in the affirmative. He (the Holy Prophet) remarked: What would you do with:" There is no god but Allah," when he would come (before you) on the Day of Judgment? He (Usama) said: Messenger of Allah, beg pardon for me (from your Lord). He (the Holy Prophet) said: What would you do with:" There is no god but Allah" when he would come (before you) on the Day of Judgment? He (the Holy Prophet) added nothing to it but kept saying: What would you do with:" There is no god but Allah," when he would come (before you) on the Day of Judgment?