Treachery of Banu Quraiza. After the expulsion of the Jews of the Banu Qainuqa' and Bani Nadeer, the Jews of Banu Quraiza alone remained in Madina. They assured the Holy Prophet of their loyalty. In the battle of the Ditch, the Banu Nadeer Jews who had been expelled by the Muslims to Khyber were in the forefront in the matter of hostility to the Muslims. Huyayy b Akhtab the leader of the Banu Nadeer opened negotiations with Banu Quraiza to attack the Muslims from behind. Ka'ab b Asad the leader of the Banu Quraiza at first hesitated, but when it was brought to him that in view of the overwhelming strength of the coalition against the Muslims, the Muslims were apt to be destroyed, the Banu Quraiza agreed to throw in their lot with the coalition against the Muslims.
Holy Prophet's emissary to Bana Quraiza. Banu Quraiza were an ally of the Aus. When the Holy Prophet came to know of the intended treachery of Banu Quraiza, he sent Sa'ad b Ma'aadh, the leader of the Aus, as an emissary to Banu Quraiza. He tried to prevail upon Banu Quraiza the desirability of remaining faithful to their pact with the Holy Prophet. In a fit of arrogance Ka'ab b Asad said, "Who is the Prophet of God ? There is no agreement between us and Muhammad." The mission of Sa'ad b Ma'aadh failed, and the position of the Muslims exposed to attack from within as well as without seemed to be precarious. The Holy Prophet, however, did not lose heart He felt confident that God would help the Muslims. And God did help the Muslims. Before Quraiza would attack the Muslims, the coalition against the Muslims withdrew and the siege was lifted.
Action against Banu Quraiza. With the disintegration of the forged united front against the Muslim, the initiative once again came to rest with the Muslims. Immediately the battle of the ditch was over, the Holy Prophet moved with his force against Banu Quraiza to chastise them for their treachery. Huyayy b Akhtab the leader of Banu Nadeer promised the Banu Quraiza every possible help, and to assure them of Banu Nadeer help he came to reside with Banu Quraiza. When the Muslims marched against Banu Quraiza, the latter shut themselves in their forts. Ka'ab b Asad the leader of Banu Quraiza advised his tribe to be converted to Islam or acknowledge the suzerainty of the Muslims. Under the influence of Huyayy b Akhtab, the Banu Quraiza did not accept the advice of their leader, and said that they would fight to the bitter end.
Fate of Banu Quraiza. The Muslim tightened the siege, and took steps to ensure that no outside help could reach Banu Quraiza. The siege lasted for a fortnight, and ultimately brought to bay, Banu Quraiza surrendered, and pleaded that the same terms should be allowed to them as had been offered to Banu Qainuqa' and Banu Nadeer before them. This was not agreed to by the Holy Prophet as he had enough of the treachery of Banu Nadeer. After further negotiations it was decided that an arbitrator should be appointed who should decide the fate of Banu Quraiza. As Ranu Quraiza were allied with the Aus, they named Sa'ad b Ma'aadh, the leader of the Aus, as the arbitrator. The Holy Prophet accordingly appointed Sa'ad b Ma'aadh as the arbitrator. On his appointment as arbitrator, Sa'ad b Ma'aadh took a pledge from both the parties that whatever decision was given by him would be binding on both the parties. After the pledge had been given, Sa'ad asked the Jews as to what was the penalty of traitors under Jewish law. It was discovered that the penalty in such cases was death. Sa'ad next posed the question whether the Jews had any pact with the Muslims. It was brought to light that there was originally such an agreement. Sa'ad then asked whether ii was a fact that they had repudiated that agreement on the occasion of the battle of the Ditch. This could not be denied by the Jews as Sa'ad had come to them as an emissary and they had told him at that time that they had no agreement with the Muslims. Sa'ad accordingly gave the award that as the Jews had acted as traitors, all the adult male Jews deserved to be killed under the Jewish law. The sentence was duly executed and that was the end of Banu Quraiza.