What is the reason for the difference in the Prophet's (peace be upon him) ruling among the three Jewish tribes (Banu Qaynuqa, Banu al-Nadir, and Banu Qurayza)? And was it possible for Sa'd ibn Mu'adh (may Allah be pleased with him) to rule with a judgment other than killing for Banu Qurayza? And does Sa'd's judgment according to what is in their Torah mean that the People of the Book are judged by their own laws?

The Prophet's, peace and blessings be upon him, treatment of Banu Qurayza differed from that of Banu Qaynuqa and Banu al-Nadir due to the varying degrees of their enmity and treachery, especially their alliance with the confederates (Al-Ahzab) against the Muslims at the most critical time. Sa'd ibn Mu'adh's judgment concerning Banu Qurayza was a matter of justice and wisdom, and it concurred with Allah's judgment, just as it concurred with the judgment of the Torah in the possession of the Jews. This ruling was a response to their great betrayal and their attempt to annihilate the Muslims, an act for which even contemporary laws prescribe punishment.