Sahih Bukhari Volume 4, Book 52, Hadith Number 271.

Narated By 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).”