Surah Al-Kahf, Ayah 20
Quran 18:20 · The Cave · Makki · Para 15 · Page 295
اِنَّهُمْ اِنْ یَّظْهَرُوْا عَلَیْكُمْ یَرْجُمُوْكُمْ اَوْ یُعِیْدُوْكُمْ فِیْ مِلَّتِهِمْ وَلَنْ تُفْلِحُوْۤا اِذًا اَبَدًا ۟
Transliteration
Innahum in yathharoo AAalaykumyarjumookum aw yuAAeedookum fee millatihim walan tuflihooithan abada
Saheeh International
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."
Al-Mukhtasar fi Tafsir
If your people discover you and find out where your whereabouts, they will kill you by stoning you, or they will force you to return to their deviated creed that you used to follow before Allah favoured you by guiding you to the true religion. If you return to that you will never succeed - not in this world nor in the Hearafter. Instead, you will suffer a great loss in both places on account of your leaving the true religion to which Allah had guided you and your returning to that deviated creed.
Tafsir Ibn Kathir (abridged)
Explains 18:19–18:20 together — read it on 18:19