Fighting for the Cause of Allah (Jihaad)

Bukhari :: Book 4 :: Volume 52 :: Hadith 271

Narrated Jabir:

The Prophet said, "Who is ready to kill Ka'b bin Ashraf (i.e. a Jew)." Muhammad bin Maslama replied, "Do you like me to kill him?" The Prophet replied in the affirmative. Muhammad bin Maslama said, "Then allow me to say what I like." The Prophet replied, "I do (i.e. allow you)."