Please read the narartion in Bukhari which says " "Ibn `Abbas told me that there were some Muslims who were with the pagans to increase their number against Allah's Messenger (and the Muslim army) so arrows (from the Muslim army) would hit one of them and kill him or a Muslim would strike him (with his sword) and kill him. So Allah revealed:

'Verily! As for those whom the angels take (in death) while they are wronging themselves (by staying among the disbelievers).' (4.97).

For more details pease read our articles on main page Shia-Sunni point of view about the Companions of The Holy Prophet.

URDU TRANSLATION: