The externed Jews of Madina and its outskirts had now openly joined hands with Abu Sufian to attack the Muslims again. While fleeing from Ohad, Abu Sufian had vowed to come back to take revenge. Prominent leaders of Bani Nazeer like Hai Bin Akhtab, Salam Bin Mushkam and Kinana Bin Alhaqiq came to Mecca, and met Abu Sufian who was already preparing for another war. With the help of Bani Guffan, Bani Asad and other mighty clans from the neighbouring areas, they raised an army of four thousand soldiers. The flag was decorated at Darun Nadva and given to Asma son of Talha Bin Talha. The general command was with Abu Sufian. As the army was marching towards Madina other tribes too joined them making an unformidable force of ten thousand soldiers. Four men of Bani Khaza-a immediately rushed to Madina and informed the Prophet (S.A.W) about the coming attack. The Prophet (S.A.W) could collect only three thousand people in this short-period and came out of the city to face them. He pitched his tents at the foot of Mount Sara. The women and children were put in safer places inside the city.

When the Muslims in the battlefield learned that Abu Sufian is coming with a force of ten thousand soldiers they became panicky and wanted to leave the battlefield. Many of them wanted to go home to protect their wives and children knowing fully well that they are not in danger. The Prophet (S.A.W) unmoved by these desertions ordered his men to dig trenches, and himself led the digging, and within seven days completed the entire task. The army of Abu Sufian on seeing the trenches were shocked. Because the idea of digging trenches was unheard of in Arabia. Unable to attack the Muslims, he ordered to lay a siege and wait.

The Muslims who were over tired with digging of trenches in extremely cold weather and cold wind blowing and without proper food, shelter and sleep had to stand in the open to face the showers of arrows from the enemies. Then the fear of attack at any moment by ten thousand well-equipped and much superior soldiers loomed large on their heads. A whole month passed in this atmosphere making the Muslims more demoralized. On that they got the news from Madina that Bani Quraiza (a Jewish tribe) with whom the Muslims had a peace pact had joined the forces of Abu Sufian. This endangered the lives of the families of the Muslims, who were left behind with no male to look after them.

The Prophet (S.A.W) in the mid of the night came to his people and asked as to who can go to the enemies and bring some news of their movements. But none came forward. The Prophet (S.A.W) then asked Abu Bakr directly to get some news of the enemies, but Abu Bakr excusing himself refused. The Prophet (S.A.W) then asked Umar to do the needful but he too refused. The Prophet (S.A.W) then asked Hozaifah who immediately went. [Tafseer Durrul Mansur Vol 5 page 185]. Suddenly Amr Ibne Abdawood along with Akrama son of Abu Jahal, Abdulla Ibne Abu Mogheera, Zarrar Ibne Khattab, Nofil Ibne Abdulla with two others crossed the trenches and stood before the Muslims challenging them.

Amr Ibne Abdawood was so famous for his bravery, valour and courage that his strength was compared to the strength of one thousand people. The terror of his personality had so frightened some of the Muslims that according to Quran, "Their hearts were petrified and were beating so violently that they were thinking of running away." They were so shocked and stunned by his presence that they became motionless as if birds were sitting on their heads. From the entire Muslim army Ali (A.S.) was the only person to accept their challenge. But the Prophet (S.A.W) did not allow Ali (A.S.) to have a bout with Amr and ordered him to go back to his position, reminding Ali (A.S.) that he was Amr Ibne Abdawood. Amr again repeated his challenge and again it was only Ali (A.S.) to answer his challenge. The Prophet (S.A.W) again ordered Ali (A.S.) back to his position. When Amr challenged the Muslims for the third time and again no Muslim went forward to accept the challenge, Ali (A.S.) came out from his position to face him. The Prophet (S.A.W) again reminded Ali (A.S.) that he is Amr Ibne Abdawood. Ali (A.S.) in reply said, "Yes I know he is Amr Ibne Abdawood." The Prophet (S.A.W) then granting permission to fight Amr tied a turban on Ali (A.S.)’s head (Ali (A.S.) generally went to fight bareheaded) and gave the famous sword Zulfiqar. As Ali (A.S.) proceeded towards Amr the Prophet (S.A.W) raised his hands and prayed, "O Allah you took away Obaida Bin Harris from me on the day of Badr, Hamza on the day of Ohad, and now it is Ali (A.S.), my brother and my uncle’s son who is left with me. Protect him O Lord as I have given him under your protection. O Allah don’t leave me alone as You are The Best Protector." Then pointing his finger towards Ali (A.S.) he said, "Here goes the embodiment of faith to face the infidel." Some of the Muslims were so sure of Ali (A.S.)’s death that they came down some distance near Ali (A.S.) to have a last view. Ali (A.S.) walked upto Amr and stood in front of him.

Amr laughed and said, "I never expected anyone under the sky who would challenge me."

Then getting down from his horse, as Ali (A.S.) was on foot, he cut the legs of his horse in anger and attacked Ali (A.S.) with a quick blow of his sword. Ali (A.S.) took the blow on his shield, but it was so severe that he got a cut on his forehead. Then Ali (A.S.)’s attack was so instant and so quick that his sword cut Amr’s shoulders and went right down. Amr fell dead and Ali (A.S.) cried Allah-o-Akbar (God is Greatest). Then severing his head Ali (A.S.) brought it before the Prophet (S.A.W) and laid it on his feet. The Prophet (S.A.W) received Ali (A.S.) with joy and said, "Ali (A.S.)’s one stroke at Khandaq is superior to the devotional prayers of both the worlds."

Abu Bakr and Umar were so happy to see Amr killed that both of them rushed to receive Ali (A.S.) and kissed his forehead. Ali (A.S.) then returned to finish the remaining members of Amr’s gang, but by then they had fled and were crossing the trenches. Ali (A.S.) caught them and finished them.

Shah Abdul Haq Muhaddis Dehlavi writing on the fight of Ali (A.S.) at Khandaq has quoted a tradition of the Prophet (S.A.W), "Ali (A.S.)’s fight at Khandaq is equal to the sacrifices my entire nation will do till the Day of Judgement."

The death of Amr shocked the enemies and shattered their hopes of wiping out the Muslims. They were now a miserable lot not knowing what to do. Then suddenly the weather changed and a fierce cold wind started blowing from the sea. For three days and nights nobody could hold their shelters nor light a fire. Abu Sufian was so disgusted with the whole atmosphere that he raised the siege and went away. Seeing the Quraish retreating the members of Bani Guftan too went away. When Amr’s sister came to the battlefield to see her brother’s corpse she was surprised to see that Ali (A.S.) had not removed a single thing from Amr’s body (it was a custom among Arabs to take away all the belongings of the deceased including the clothes) praising Ali (A.S.) she said, "Whoever has killed my brother belongs to a noble family." Then she composed a verse in praise of Ali (A.S.) which says, "If anyone other than Ali had killed my brother I would have wept my whole life over the infamy. But now I will not cry."

In all the three wars of Badr, Ohad and Khandaq, Ali (A.S.) alone had killed seventy persons, all of whom were either the heads of some clan or a famous warrior of Arabia.

After returning from the battlefield the Prophet (S.A.W) sent some three thousand men under the command of Ali (A.S.) to punish the tribe of Bani Quraiza who had broken the pledge with the Muslims and had supported Abu Sufian, just when the Muslims were besieged by him. Ali (A.S.) went straight to their fort and fixed his flag on their gate. An observer from their fort who recognized Ali (A.S.) cried, "The killer of Amr Ibne Abdawood has come", another voice answered, "He has not killed Amr but broken our backs" and some were cursing the Prophet (S.A.W). Ali (A.S.) in answer to their curses and cries said, "By Allah either will I conquer your fort or die and meet my uncle Hamza." The Jews then came out of the fort to fight with Ali (A.S.) and his men. Ali (A.S.) fought and killed all their leaders. The Prophet (S.A.W) ordered to kill Hai Ibne Akhtab also who had instigated the Jews not to leave Madina. When Ali (A.S.) went near Hai he said, "I am happy to be killed by a noble man like you." Ali (A.S.) replied,"Yes only noble people kill bad men and bad men harass noble people."

The fate of the Jewish tribes of Bani Nazeer and Bani Quraiza had dampened the hopes of the Jewish tribes of Khaiber who were nursing the idea of regaining the hold of Madina. Finding themselves unable to achieve this goal they instigated Bani Saad to Fadak near Khaiber to challenge the Muslims. The Prophet (S.A.W) on getting the news sent Ali (A.S.) with a hundred people to probe the situation. Ali (A.S.) travelled only during the night and hiding himself during the day reached a homage a place between Fadak and Khaiber. There he met an emissary of Bani Saad who was going to deliver some message to the Jews of Khaiber. On questioning, he confessed that he was going to inform them that two hundred men were ready with their arms to attack the Muslims. Ali (A.S.) immediately rushed to finish those people but they had received the news of Ali (A.S.)’s coming and had fled, leaving behind fifty camels and two thousand goats. Ali (A.S.) brought them and presented them to the Prophet (S.A.W).