In Mohammed's own words, as related by Abu Abdullah Muhammad bin Ismail bin Ibrahim bin al-Mughira al-Ja'fai, AKA Bukhari:
Allahs Apostle said, Who is willing to kill Kab bin Ashraf who has hurt Allah and His Apostle? Thereupon Muhammad bin Maslamah got up saying, O Allahs Apostle! Would you like me to kill him? The Prophet said, Yes, Maslamah said, Then allow me to say false things in order to deceive him. The Prophet said, You may say such things.
The father of lies and the prophet of the father of lies.