Indeed, if they come to know of you, they will stone you or return you to their religion. And never would you succeed, then - ever."
The Saheeh International Quran Translation
إِنَّهُمْ إِن يَظْهَرُوا۟ عَلَيْكُمْ يَرْجُمُوكُمْ أَوْ يُعِيدُوكُمْ فِى مِلَّتِهِمْ وَلَن تُفْلِحُوٓا۟ إِذًا أَبَدًاIndeed, if they come to know of you, they will stone you or return you to their religion. And never would you succeed, then - ever."