**Kab b. al-Ashraf **
Angered by the poems, Muhammad had had enough. He asked, “Who would rid me of [Kab]?” Five Muslims volunteered, one of whom was Kab’s foster-brother named Abu Naila. They informed him, “O apostle of God [Muhammad], we shall have to tell lies.” He answered, “Say what you like, for you are free in the matter.” They set upon a clever plan.
The signal to kill was as follows: Abu Naila would run his hand through Kab’s hair, complimenting him on his perfume, three times. This he did, yelling, “Smite the enemy of God!” Kab mounted a strong defense, so their swords were ineffective. Finally, one of the conspirators remembered his dagger, stabbed Kab in the belly, and then bore it down until it reached Kab’s genitals, killing him.
They made it back to Muhammad, saluted the prophet as he stood praying, and he came out to them. They told him that the mission was accomplished. He spat on their comrade’s wound, and they returned to their families. Their attack on Kab sent shock waves into the Jewish community, so that “there was no Jew in Medina who did not fear for his life,” reports Ibn Ishaq.
Muslim historian Tabari reports that the five Muslim thugs severed Kab’s head and brought it to Muhammad.
Sources: Bukhari vol. 5, no. 4037; Muslim vol. 3, no. 4436; Ibn Ishaq 364-69 / 548-53; Tabari, The History of al-Tabari, Vol. VII, trans. W. Montgomery Watt (SUNYP, 1987), pp. 94-98 / 1368-73.