Prohibition of alliance with disbelievers

وَمَا كُنتَ تَرْجُوٓا۟ أَن يُلْقَىٰٓ إِلَيْكَ ٱلْكِتَـٰبُ إِلَّا رَحْمَةً مِّن رَّبِّكَ ۖ فَلَا تَكُونَنَّ ظَهِيرًا لِّلْكَـٰفِرِينَ

And you were not expecting that the Book would be conveyed to you, but [it is] a mercy from your Lord. So do not be an assistant to the disbelievers.