Surah Al-Ma'idah 5:51

۞ يَـٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوا۟ لَا تَتَّخِذُوا۟ ٱلْيَهُودَ وَٱلنَّصَـٰرَىٰٓ أَوْلِيَآءَ ۘ بَعْضُهُمْ أَوْلِيَآءُ بَعْضٍ ۚ وَمَن يَتَوَلَّهُم مِّنكُمْ فَإِنَّهُۥ مِنْهُمْ ۗ إِنَّ ٱللَّهَ لَا يَهْدِى ٱلْقَوْمَ ٱلظَّـٰلِمِينَ

O you who have believed, do not take the Jews and the Christians as allies. They are [in fact] allies of one another. And whoever is an ally to them among you - then indeed, he is [one] of them. Indeed, Allāh guides not the wrongdoing people.

Translation: Saheeh International

Tafsir

O you who believe do not take Jews and Christians as patrons affiliating with them or showing them affection; they are patrons of each other being united in disbelief. Whoever amongst you affiliates with them he is one of them counted with them. God does not guide the folk who do wrong by affiliating with disbelievers.

Excerpt from Tafsir al-Jalalayn, commentary on 5:51, via Quran.com. The reader has the full commentary and 9 more tafsirs.