Sahih Bukhari Volume 009, Book 083, Hadith Number 029.
Narrated By Salama : We went out with the Prophet to Khaibar. A man (from the companions) said, "O 'Amir! Let us hear some of your Huda (camel-driving songs.)" So he sang some of them (i.e. a lyric in harmony with the camels walk). The Prophet said, "Who is the driver (of these camels)?" They said, "Amir." The Prophet said, "May Allah bestow His Mercy on him !" The people said, "O Allah's Apostle! Would that you let us enjoy his company longer!" Then 'Amir was killed the following morning. The people said, "The good deeds of 'Amir are lost as he has killed himself." I returned at the time while they were talking about that. I went to the Prophet and said, "O Allah's Prophet! Let my father be sacrificed for you! The people claim that 'Amir's good deeds are lost." The Prophet said, "Whoever says so is a liar, for 'Amir will have a double reward as he exerted himself to obey Allah and fought in Allah's Cause. No other way of killing would have granted him greater reward."