Sayyiduna Abu Hurayrah (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "No one is wounded in the way of Allah, and Allah knows best who is wounded in His way, except that when he comes on the Day of Resurrection his wound will be flowing with blood, its colour the colour of blood and its scent the scent of musk."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18528