Surah An-Nisa' (The Women), Verse 144

یٰۤاَیُّهَا الَّذِیْنَ اٰمَنُوْا لَا تَتَّخِذُوا الْكٰفِرِیْنَ اَوْلِیَآءَ مِنْ دُوْنِ الْمُؤْمِنِیْنَ اَتُرِیْدُوْنَ اَنْ تَجْعَلُوْا لِلّٰهِ عَلَیْكُمْ سُلْطٰنًا مُّبِیْنًا ۟

Yaaa aiyuhal lazeena aamanoo laa tattakhizul kaafireena awliyaaa'a min doonil mu'mineen; aturee doona an taj'aloo lillaahi 'alaikum sultaanam mubeenaa

“O ye who believe! Take not for friends unbelievers rather than believers: Do ye wish to offer Allah an open proof against yourselves?”

Quran 4:144 (Yusuf Ali Translation)