الآية رقم (51) - يَا أَيُّهَا الَّذِينَ آمَنُواْ لاَ تَتَّخِذُواْ الْيَهُودَ وَالنَّصَارَى أَوْلِيَاء بَعْضُهُمْ أَوْلِيَاء بَعْضٍ وَمَن يَتَوَلَّهُم مِّنكُمْ فَإِنَّهُ مِنْهُمْ إِنَّ اللّهَ لاَ يَهْدِي الْقَوْمَ الظَّالِمِينَ

(51) - (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, Allah guides not the wrongdoing people.)

Reason of revelation:

It was said that this verse was revealed because of Obada bin Assamed (may Allah be pleased with him) and Abdullah bin Obay bin Salool, for Obada stopped his allegiances with the Jews, but Abdullah kept his allegiances claiming the he feared that the disbelievers might defeat the Muslims. This divine warning was directed to the hypocrites in Medina whose faithfulness was for the Jews against the Prophet (saws), so their loyalty was to the Jews rather than to Muslims.

(  إِنَّ اللَّهَ لَا يَهْدِي الْقَوْمَ الظَّالِمِينَ ) (…Indeed, Allah guides not the wrongdoing people): Because they were wrongdoers, they were deprived from divine support, whereas the guidance is for all humans.