It is narrated from Sayyiduna Jabir (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "Who will kill Ka'b bin al-Ashraf? He has harmed Allah and His Messenger." Muhammad bin Maslamah (may Allah be pleased with him) said: O Messenger of Allah! Would you like me to kill him? He (peace and blessings be upon him) said: "Yes." Then the Companion (may Allah be pleased with him) said: Grant me (peace and blessings be upon him) permission. He (peace and blessings be upon him) said: "I have given you permission." Then he narrated the story of the killing of Ka'b bin al-Ashraf: when I had killed him, they came to the Prophet (peace and blessings be upon him) and informed him (peace and blessings be upon him), and the Prophet (peace and blessings be upon him) said: "War is deception."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13280