Musnad Ahmad Hadith 27503

It is narrated from Abu Darda (may Allah be pleased with him) that the Prophet (ﷺ) said: Allah Almighty will not combine the dust of striving in the way of Allah and the smoke of Hell in the belly of a man. Whoever's feet become dusty in the path of Allah, Allah will make his whole body forbidden to the Fire. Whoever fasts for one day in the way of Allah, Allah distances Hell from him by a distance of one thousand years, which a swift rider could cover. Whoever receives a wound or suffers pain in the way of Allah, on the Day of Resurrection it will come forth flowing even more, but on that day its color will be like saffron and its fragrance like musk. And whoever receives a wound in the way of Allah, a seal of the martyrs is placed upon it, and the first and the last will recognize him by it and say: This is the man with the seal of the martyrs. And any Muslim who fights in the way of Allah for the time it takes for milk to flow from a she-camel’s teats, Paradise becomes obligatory for him.