It is narrated from Sayyiduna Abu Umamah (may Allah be pleased with him) that Sayyiduna Abu Dharr (may Allah be pleased with him) said: O Messenger of Allah! What is charity? He said: "A reward multiplied many times over, and with Allah there is even more." Then he (peace and blessings be upon him) recited this verse: "Who is it that will lend Allah a goodly loan so that He may multiply it for him many times over?" [Surah al-Baqarah: 245].
He said: O Messenger of Allah! Which charity is the best? He said: "Charity given secretly to a needy person, or charity that comes from the effort of one who has little," then he (peace and blessings be upon him) recited this verse: "If you disclose your charities, that is good; but if you conceal them and give them to the poor, that is better for you" [Surah al-Baqarah: 271].
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 7860