There are several incidents that bear witness to the cruel nature of Muhammad.
The mass execution of the Jewish tribe Banu Qurayza remains one of the most contentious episodes in the life of Muhammad.
According to the earliest Islamic biographies (Sira), such as those by Ibn Ishaq and Ibn Hisham, the tribe was accused of conspiring with the Meccan Quraish during the Battle of the Trench. After a 25-day siege, the tribe surrendered.
Sa'd ibn Mu'adh, an ally of the tribe who had been wounded in battle, was appointed as arbitrator. He ruled that the men be killed and the women and children enslaved.
Ibn Hisham, Sira: Records that after the Battle of the Trench, the men of the tribe (600-900) were executed by order of a mediator chosen by the tribe itself, Sad ibn Muadh.
A group of men from the Ukayl and Urayna tribes came to Medina, converted, but later killed a shepherd and stole camels.
Muhammad ordered their hands and feet cut off, their eyes branded with heated irons, and left them in the desert heat to die while denying them water.
Early sources like Ibn Sa'd's Kitab al-Tabaqat al-Kabir describe the assassinations of poets who mocked Muhammad. Asma bint Marwan was reportedly killed in her sleep while nursing her child, and the elderly Abu Afak was killed for his satirical verses.
Surah 5:33, which mandates severe punishments for those who "wage war against Allah and His Messenger":
"The punishment of those who wage war against Allah and His Messenger... is only this, that they should be murdered or crucified or their hands and their feet should be cut off on opposite sides..."
The "cruelty" of the Banu Qurayza massacre is not merely an isolated military decision, but a reflection of a system that merges religious authority with coercive state power.
Muhammad acted as a sovereign judge who utilized the sword to punish treason and establish a political-religious order, as seen in the mass execution of the Banu Qurayza. The Gospels portray Jesus Christ as the "Prince of Peace" who consistently renounced violence, famously commanding his followers to "love your enemies" and choosing to heal his captors and forgive his executioners while on the Cross.
While Muhammad used the power of the state to execute judgment upon his enemies, Jesus used his own execution to offer mercy to a fallen world, signaling that His kingdom was not of this world.