Quran 5:61 from Surah Al-Maaida on Divine Marvels.
وَإِذَا جَآءُوكُمۡ قَالُوٓاْ ءَامَنَّا وَقَد دَّخَلُواْ بِٱلۡكُفۡرِ وَهُمۡ قَدۡ خَرَجُواْ بِهِۦۚ وَٱللَّهُ أَعۡلَمُ بِمَا كَانُواْ يَكۡتُمُونَ
English translation: And when they come to you they say We believe But certainly they entered with disbelief and they certainly went out with it And Allah knows best [of] what they were hiding
Transliteration: wa-idha jaukum qalu amanna waqad dakhalu bil-kuf'ri wahum qad kharaju bihi wal-lahu a'lamu bima kanu yaktumuna