Musnad Ahmad 30:2071

'Abd al-Samad ibn Hassan narrated to us, he said: Sufyan informed us, from al-A'mash, from Dhakwan, from Abu Hurairah, he said: The Messenger of Allah, peace and blessings of Allah be upon him, said: "No servant is wounded in the way of Allah—and Allah knows best who is wounded in His way—except that his wound will come on the Day of Resurrection, its color being the color of blood, and its scent being the scent of musk."