وَلَنْ تَرْضَىٰ عَنكَ ٱلْيَهُودُ وَلَا ٱلنَّصَـٰرَىٰ حَتَّىٰ تَتَّبِعَ مِلَّتَهُمْ ۗ قُلْ إِنَّ هُدَى ٱللَّهِ هُوَ ٱلْهُدَىٰ ۗ وَلَئِنِ ٱتَّبَعْتَ أَهْوَآءَهُم بَعْدَ ٱلَّذِى جَآءَكَ مِنَ ٱلْعِلْمِ مَا لَكَ مِنَ ٱللَّهِ مِن وَلِىٍّ وَلَا نَصِيرٍ

Translation (Sahih International):
"And never will the Jews or the Christians approve of you until you follow their religion. Say, 'Indeed, the guidance of Allah is the [only] guidance.' If you were to follow their desires after what has come to you of knowledge, you would have against Allah no protector or helper."