Surah Ali 'Imran 3:100

يَـٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوٓا۟ إِن تُطِيعُوا۟ فَرِيقًا مِّنَ ٱلَّذِينَ أُوتُوا۟ ٱلْكِتَـٰبَ يَرُدُّوكُم بَعْدَ إِيمَـٰنِكُمْ كَـٰفِرِينَ

O you who have believed, if you obey a party of those who were given the Scripture, they would turn you back, after your belief, [to being] unbelievers.

Translation: Saheeh International

Tafsir

The following was revealed when the Jews passed by the Aws and the Khazraj and were infuriated by their comradeship and set about reminding them of their mutual hostility in the days before Islam such that they caused them to quarrel and the two tribes were on the verge of fighting one another O you who believe if you …

Excerpt from Tafsir al-Jalalayn, commentary on 3:100, via Quran.com. The reader has the full commentary and 9 more tafsirs.