Musnad Ahmad

It is narrated from Sayyiduna ‘Irbaad (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: “There will be a dispute before the Lord of the worlds regarding those who die in the plague, between the martyrs and those who die a natural death. The martyrs will say: ‘These are our brothers; they were martyred like us.’ And those who die a natural death will say: ‘These are our brothers and were martyred on their beds like us.’ The Lord will say: ‘Look at their wounds. If their wounds are like the wounds of the martyrs, then they will be counted among the martyrs and will be with them.’ When it will be seen, their wounds will resemble the wounds of the martyrs.”