Sahih Muslim Book 5, Hadith Number 2228.

Chapter : Proof of reward for the giver of charity even if it goes into the hands of and undeserving person.

Abu Haraira reported that the Messenger of Allah (may peace be upon him) gave similitude’s of a miserly man and the giver of charity as two persons who have two coats-of-mail over them with their hands pressed closely to their breasts and their collar bones. Whenever the giver of charity gives charity it (the coat-of mail) expands so much as to cover his finger tips and obliterate his foot prints. And whenever the miserly person intends to give charity (the coat-of-mail) contracts and every ring grips the place where it is. He (Abu Huraira) said: I saw the Messenger of Allah (may peace be upon him) saying with fingers in the opening of his shirt: “If you had seen him trying to expand it, it will not expand.”