Here the Qur’an mentions the controversy that took place with the Jews (People of the Book) in Medina, and reveals the beginning of their conspiracy against the Muslims after the emigration, The Jews were trying by various means, either through discussion or by presenting the alleged evidence from their distorted Torah, to cast doubt on everything that the Prophet, (saws), brought.

So Allah (swt) has warned His faithful servants not to obey a group of those who were given the Scripture, who envy the believers for what Allah (swt) has given them of His bounty, and for what He has honored them with by sending His Messenger, as Allah (swt) said in Surah Al-Baqarah:

وَدَّ كَثِيرٌ مِّنْ أَهْلِ الْكِتَابِ لَوْ يَرُدُّونَكُم مِّن بَعْدِ إِيمَانِكُمْ كُفَّاراً حَسَدًا مِّنْ عِندِ أَنفُسِهِم مِّن بَعْدِ مَا تَبَيَّنَ لَهُمُ الْحَقُّ 

{Many of the People of the Scripture wish they could turn you back to disbelief after you have believed, out of envy from themselves [even] after the truth has become clear to them.} (Al-Baqara: 109)

Reason of Revelation:

Zaid bin Aslam said: A Jew named Shas bin Qais – who was an old man of great infidelity and severe hostile to Muslims – passed by a group from Aws and Khazraj who gathered to talk, so he was angry about what he saw of their familiarity and the reconciliation between them in Islam after the enmity that existed between them before became Muslims, so he said: The people of Banu Qila (meaning the Aws and Khazraj) have gathered in this country?! No, by Allah, we have no decision with them if they meet with each other, so he ordered a young man from among the Jews who was with him, and said to him: go to them and sit with them, remind them of the day of (Boath) and what was before it, and narrate to them some of what they used to say of poetry. (Boath) was the day when the Aws fought Khazraj, where the Aws won over the Khazraj. So he did and spoke.

Then the people spoke at that, and they quarreled and bragged until two men from the two groups, Aws bin Qibti, one of Children of Haritha from the Aws, and Jabbar bin Sakhr, one of children of Salamah from the Khazraj. They argued, then one of them said to his companion: If you wish, by Allah, I will put it back now as it was (in its youth). The two groups were all angry and said: We did, weapon, weapon, your appointment at Alzahira, so they went out to it, and the Aws and Khazraj agreed on their claim that they were upon in the pre-Islamic era. The Messenger of Allah (saws) was informed of that, and he went out to them among those who were with him of the Almuhajereen (immigrants), when arrived to them, he (saws) said:

{“Oh Muslims, are you imitating the behavior of the days of ignorance while I am among you after Allah (swt) honored you with Islam and cut off the pre-Islamic matter from you and brought you together? Are you going back to what you used to be as disbelievers?! Allah, Allah”}

So the people knew that it was an evil whisper (from Satan) and a plot from their enemy, so they threw the weapons from their hands, and cried and hugged each other, then they left with the Messenger of Allah (saws), obedient to him. Then Allah (swt) sent down to them this verse. Jaber said: “I have never seen a day worse at the beginning, and better at the end than that day.”

This is what the Jews did in the days of the Prophet Mohammed (saws), and every separation happen in the Arab and Islamic nation, the Jews are behind them, the grandchildren of those grandparents.