After the Muslims had repelled the Pagans at the Battle of the Trench, Muhammad turned on the Jewish tribe of Medina known as the Banu Qurayza.
The Banu Qurayza had planned to defect to the enemy during the Battle of the Trench but in the end they decided against it. According to Sahih Bukhari, it was the Angel Gabriel that actually commanded Muhammad to attack them (Sahih Bukhari, book 52, #68). In revenge for their planned treachery, Muhammad ordered a siege of their fortress. After 25 days they were forced to surrender. Muhammad then ordered that ditches be dug in the main square of Medina, all of the men of the tribe were then tied up and brought out in front of Muhammad and his companions in batches, they were beheaded one by one and thrown into the ditches. (Abu Dawud 38:4390) Between 600-900 male members of the tribe were beheaded in this way. (Tabari, vol viii, pp.35-36, Ibn Ishaq, pg. 461-464) Also amongst them was the chief of the Banu Nadir, Huyayy ibn Akhtab. He remained defiant to the end, before he was beheaded he was led in front of Muhammad with his hands tied to his neck, he told Muhammad that he did not regret being his enemy. Only one of the women of the Banu Qurayza was killed, (Abu Dawud 14:2665) the rest were taken as slaves along with the children. Muhammad himself took Rayhana as his slave, he proposed that she convert to Islam and marry him, but Rayhana refused the proposal and instead kept her Jewish faith, remaining Muhammad’s slave and concubine. (Ibn Ishaq, pg. 466)