Sahih Bukhari Volume 009, Book 089, Hadith Number 295.
Narrated By Um Salama : The Prophet heard the voices of some people quarreling near his gate, so he went to them and said, "I am only a human being and litigants with cases of disputes come to me, and maybe one of them presents his case eloquently in a more convincing and impressive way than the other, and I give my verdict in his favor thinking he is truthful. So if I give a Muslim's right to another (by mistake), then that (property) is a piece of Fire, which is up to him to take it or leave it." (See Hadith No. 281)