The Banū Aws (Arabic: بنو أوس pronounced [ˈbænuː ʔæws], "Sons of Aws") or simply Aws (Arabic: أوس; also Romanized as Aus) was one of the main Arab tribes of Medina. The other was Khazraj, and the two, constituted the Ansar ("helpers [of Muhammad]") after the Hijra.
About 300 A.D., during the emigration of Kahlān from Yemen prior to the Great Flood of Maʼrib Dam, Thaʻlaba bin ʻAmr, grand father of al-Aws, separated from his tribe and settled in Yathrib (Medina), which was then controlled by Jewish clans, and Banū Qayla were subordinate to the Jews for some time, until Mālik bin ʻAjlān of Khazraj asserts independence of the Jews, so Aws and Khazraj obtained a share of palm-trees and strongholds. Thus, about 5th century, Banū Qayla took control of Yathrib and Jews retired into the background for about a century.
During these periods before Hijra, Abū Qays al-Aslat of the clan of Wāʼil, the leader of Aws, gave away the leadership to Ḥuḍayr bin Simāk of ʻAbd al-Ashhal. After a serious defeat, ʻAbd al-Ashhal and Ẓafar were withdrawn from Yathrib. The opposing leader, ʻAmr bin Nuʻmān of the Khazrajite clan of Bayāḍa, drove the Jews tribes of Banū Qurayẓa and Banū Naḍīr into alliance of the two. Nomads of Muzayna joined them too. Most of the Khazraj[n 1] as well as the Jews tribe Banū Qaynuqāʻ and the nomadic Juhayna and Ashjaʻ suppurted ‘Amr bin Nu‘mān. The Awsite clan of Ḥāritha remained neutral. Then, about 617 A.D., The Battle of Buʻāth began: Aws forced back at first, but finally defeated their opponents. The leaders of both sides were killed.
Shi'a sources say they were Jews, while a Jewish source says they and the Banu Khazraj were Arab tribes from Yemen who came to Medina in the fourth century CE. The Jewish source continues to say that the two tribes took the power of Medina from the Jews in the fifth century "By calling in outside assistance and treacherously massacring at a banquet". However, all sources agree that the Banu Aus and Banu Khazraj became hostile to each other.
A Shi'a source states that they had been fighting for one hundred and twenty years and were sworn enemies. The Jewish source states that they went to war against each other in the Battle of Bu'ath a few years before the Islamic prophet Muhammad migrated to Medina.
There were many Jewish tribes then present in Medina: Banu Nadir, Banu Qurayza, Banu Qaynuqa and many more. During the battle, The Banu Nadir and the Banu Qurayza fought with the Banu Aus, while the Banu Qaynuqa were allied with the Banu Khazraj. The latter were defeated after a long and desperate battle.
Hijrah — 622
Muhammad came to Medina as a mediator, invited to resolve the feud between the factions of Banu Aws and Banu Khazraj. He ultimately did so by absorbing both factions into his Muslim community, forbidding bloodshed among Muslims.
The Banu Aus were included in point 30-31 of the Constitution of Medina as allies to the Muslims, being as "one nation/community with the Believers". After this, Banu Aus and others became known as the Ansar.
Banu Qurayza — 627
The Banu Qurayza were a Jewish tribe who lived in Medina. The bulk of the tribe's men, apart from a few who converted to Islam, were killed in 627 CE, following a siege mounted by Muslim inhabitants of Medina and immigrants from Mecca after Banu Qurayza had agreed to aid their Meccan enemies in their attack on Medina, which the Muslims had just repulsed in the Battle of the Trench.
Since Banu Qurayza was an ally of the Banu Aus during the Battle of Bu'ath, they choose Sa'ad ibn Mua'dh, the chief of the Banu Aus  as their judge. He, in spite of the pleading of his own tribe, condemned the men to death and the women and children to slavery. Sa'ad ibn Mua'dh himself died shortly after the event, due to injuries received during the Battle of the Trench.
On 624 Muhammad ordered the assassination of Ka'b ibn al-Ashraf. According to Ibn Ishaq, Muhammad ordered his followers to kill Ka'b because he "had gone to Mecca after Badr and inveighed against Muhammad. He also composed verses in which he bewailed the victims of Quraysh who had been killed at Badr. Shortly afterwards he returned to Medina and composed amatory verses of an insulting nature about the Muslim women". This killing was carried out by the Banu Aus 
When men of the Banu Aus tribe murdered Ka'b ibn al-Ashraf, some Khazraj tribesman including Abdallah ibn Unais went to Muhammad and received a permission to put to death the person responsible for the killing of Sallam ibn Abu al-Huqayq, who was killed during the Expedition of 'Abdullah ibn 'Atik.
Sallam ibn Abu al-Huqayq (Abu Rafi) was a Jew, who helped the troops of the Confederates and provided them with a lot of wealth and supplies, on the one hand  and used to mock Muhammad with his poetry, on the other. When the Muslims had settled their affair with Banu Quraiza; Al-Khazraj tribe, a rival of Al-Aws, asked for Muhammad's permission to kill him (which Muhammad accepted) in order to merit a virtue equal to that of Al-Aws who had killed Ka'b ibn al-Ashraf.
- Sa'ad ibn Mua'dh - head 
- Bashir ibn Sa'ad leader 
- Usaid bin Hudair bin Sammak 
- Sa‘d bin Khaithamah bin Al-Harith 
- Rifa‘a bin ‘Abdul Mundhir bin Zubair 
- except ʻAbd Allāh bin Ubayy and another Khazraj leader
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