"O you who have believed, do not take the Jews and the Christians as allies" meaning: in religion. "And whoever among you takes them as allies" in religion, "then indeed, he is one of them."
﴿يَا أَيهَا الَّذِينَ آمَنُوا لَا تَتَّخِذُوا الْيَهُودَ وَالنَّصَارَى أَوْلِيَاء﴾ أَيْ: فِي الدِّينِ ﴿وَمَنْ يَتَوَلَّهُمْ مِنْكُم﴾ فِي الدِّينِ ﴿فَإِنَّهُ مِنْهُمْ﴾.