After Islam had set their affairs straight and they had become united, a Jewish man passed by a gathering of Aws and Khazraj, and he was bothered by their friendship and unity. So he sent a man who was with him to sit amongst them and remind them of the wars that used to be waged between them. He did that and kept doing it until they were provoked and became angry with one another, and they got riled up and started shouting their slogans and calling for their weapons, and threatening to go out to the Harrah (a place in Madeenah) to fight. News of this reached the Prophet (peace and blessings of Allaah be upon him), so he came to them and started to calm them down, and said, “Are you issuing the calls of the jaahiliyyah when I am still among you?” Then he recited to them the following verse (Interpretation of the meaning):
“And hold fast, all of you together, to the Rope of Allaah (i.e. this Qur’aan), and be not divided among yourselves, and remember Allaah’s Favour on you, for you were enemies one to another but He joined your hearts together, so that, by His Grace, you became brethren (in Islamic Faith), and you were on the brink of a pit of Fire, and He saved you from it. Thus Allaah makes His Ayaat (proofs, evidences, verses, lessons, signs, revelations, etc.,) clear to you, that you may be guided”
[Aal ‘Imraan 3:103]
When the Messenger of Allaah (peace and blessings of Allaah be upon him) recited this verse to them, they regretted what they had done, and they reconciled and put aside their weapons.