It has been reported on the authority of Salama bin Akwa who said: On the day of the Battle of Khaibar my brother fought a fierce fight by the side of the Messenger of Allah ﷺ . His sword rebounded and killed him. The Companions of the Messenger of Allah ﷺ talked about his death and doubted (whether it was martyrdom). (They said): (He is) a man killed by his own weapon, and expressed doubt about his affair. Salama said: When the Messenger of Allah ﷺ returned from Khaibar, I said: Messenger of Allah, permit me that I may recite to you some rajaz verses. The Messenger of Allah ﷺ permitted him. Umar bin Khattab said: I know what you will recite. I recited:
By God, if God had guided us not,
We would have neither been guided aright nor practised charity,
Nor offered prayers.
The Messenger of Allah ﷺ said: What you have said is true, I (continued):
And descend on us peace and tranquillity
And keep us steadfast if we encounter (with our enemies)
And the polytheists have rebelled against us.
When I finished my rajaz, the Messenger of Allah ﷺ said: Who composed these verses? I said: They were composed by my brother. The Messenger of Allah ﷺ said: May God show mercy to him! I said: By God, some people are reluctant to invoke Gods mercy on him (because) they say he is a man who died by his own sword. (Hearing this) the Messenger of Allah ﷺ said: He died as Gods devotee and warrior. Ibn Shihab has said: I asked one of the sons of Salama bin Akwa about (the death of Amir). He related to me a similar tradition except that he said: When I said some people were reluctant invoke Gods blessings on him, the Messenger of Allah ﷺ said: They lied. (Amir) died as Gods devotee and warrior (in the cause of Allah). For him there is a double reward, and he pointed out this by putting his two fingers together.