It is narrated from Sayyiduna Sahl bin Hunayf (may Allah be pleased with him) 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 slave in (paying for) his freedom, Allah will shade him in His shade on the Day when there is no shade but His shade."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 5569