Sahih Muslim Book 020, Hadith Number 4509.
Chapter : Acceptance of gifts on the part of state officers is forbidden.
It has been narrated on the authority of Abu Humaid as-Sa'idi who said: The Messenger of Allah (may peace be upon him) appointed a man from the Asad tribe who was called Ibn Lutbiyya in charge of Sadaqa (i.e. authorised high to receive Sadaqa from the people on behalf of the State. When he returned (with the collections), he said: This is for you and (this is mine as) it was presented to me as a gift. The narrator said: The Messenger of Allah (may peace be upon him) stood on the pulpit and praised God and extolled Him. Then he said: What about a State official whom I give an assignment and who (comes and) says: This is for you and this has been presented to me as a gift? Why didn't he remain in the house of his father or the house of his mother so that he could observe whether gifts were presented to him or not. By the Being in Whose Hand is the life of Muhammad, any one of you will not take anything from it but will bring it on the Day of Judgment, carrying on his neck a camel that will be growling, or a cow that will be bellowing or an ewe that will be bleating. Then he raised his hands so that we could see the whiteness of his armpits. Then he said twice: O God, I have conveyed (Thy Commandments).