Riyad as-Salihin

Abu Umamah (May Allah be pleased with him) reported: The Messenger of Allah (ﷺ) said, "The best of charities is to provide canopy in the Cause of Allah, to pay wages to a servant in the way of Allah, and to provide a camel in the way of Allah (to be used by a Mujahid)."

[At-Tirmidhi].