Al-Baqarah · 2:120

120. Allah addresses and warns His Prophet, telling him that the Jews and the Christians will never be happy with him unless he leaves Islam and follows what they do; and that if he, or one of his followers, were to do such a thing, after the clear truth has come to them, they would not find protection or help from Allah. This makes clear the seriousness of leaving the truth and of following people of falsehood.