Musnad Ahmad 30:3805

Hashim narrated to us, Shareek narrated to us, from al-A’mash, from Abu Salih, from Abu Hurairah, from the Prophet (peace and blessings of Allah be upon him), who said: "Whoever is wounded in the way of Allah—and Allah knows best who is wounded in His way—will come on the Day of Resurrection with the color of his wound being the color of blood, and its scent being the scent of musk."