It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) as a marfu' report (attributed to the Prophet); he said: The Messenger of Allah (peace and blessings be upon him) said: "Do you know which charity is the best?" The Companions said: Allah and His Messenger know best. He said: "The best charity is lending: lending a dirham, or lending the back of a riding animal (for use)."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9993