Sahih Bukhari Volume 008, Book 076, Hadith Number 500.
Narated By Sa'd bin Sahl As-Sa'idi : The Prophet looked at a man fighting against the pagans and he was one of the most competent persons fighting on behalf of the Muslims. The Prophet said, "Let him who wants to look at a man from the dwellers of the (Hell) Fire, look at this (man)." Another man followed him and kept on following him till he (the fighter) was injured and, seeking to die quickly, he placed the blade tip of his sword between his breasts and leaned over it till it passed through his shoulders (i.e., committed suicide)." The Prophet added, "A person may do deeds that seem to the people as the deeds of the people of Paradise while in fact, he is from the dwellers of the (Hell) Fire: and similarly a person may do deeds that seem to the people as the deeds of the people of the (Hell) Fire while in fact, he is from the dwellers of Paradise. Verily, the (results of) deeds done, depend upon the last actions."