Sayyiduna Sahl (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) said: "Whoever helps a mujahid in the path of Allah, or a debtor in his hardship, or a mukatab in (freeing) his neck, Allah Almighty will shade him in His shade on the Day when there is no shade but His shade." Amr bin Thabit added the words: "or a warrior (ghazi)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب المكاتب / 21621