Surah Ali 'Imran — Ayah 149 (3:149)
يَٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوٓاْ إِن تُطِيعُواْ ٱلَّذِينَ كَفَرُواْ يَرُدُّوكُمۡ عَلَىٰٓ أَعۡقَٰبِكُمۡ فَتَنقَلِبُواْ خَٰسِرِينَ ١٤٩
English translation (Saheeh International)
O you who have believed, if you obey those who disbelieve, they will turn you back on your heels, and you will [then] become losers.
Brief commentary
O you who have faith in Allah and follow His Messenger, if you obey the disbelieving Jews, Christians and idolaters in the misguidance they instruct you in, then you will return after your faith back to the disbelief you were upon, and you will become losers in this world and in the Afterlife.