Sahih Muslim Book 20, Hadith Number 4629.

Chapter : The merit of Jihad and campaigning in the way of Allah.

It has been narrated on the authority of Abu Huraira that the Messenger of Allah (may peace be upon him) said: One who is wounded in the way of Allah-and Allah knows better who is wounded in His way-will appear on the Day of Judgment with his wound bleeding. The colour (of its discharge) will be the colour of blood, (but) its smell will be the smell of musk.