Quran 63:3 from Surah Al-Munaafiqoon on Divine Marvels.
ذَٰلِكَ بِأَنَّهُمۡ ءَامَنُواْ ثُمَّ كَفَرُواْ فَطُبِعَ عَلَىٰ قُلُوبِهِمۡ فَهُمۡ لَا يَفۡقَهُونَ
English translation: That (is) because they believed then they disbelieved; so were sealed [upon] their hearts so they (do) not understand
Transliteration: dhalika bi-annahum amanu thumma kafaru fatubi'a ala qulubihim fahum la yafqahuna