Quran 68:51 from Surah Al-Qalam on Divine Marvels.
وَإِن يَكَادُ ٱلَّذِينَ كَفَرُواْ لَيُزۡلِقُونَكَ بِأَبۡصَٰرِهِمۡ لَمَّا سَمِعُواْ ٱلذِّكۡرَ وَيَقُولُونَ إِنَّهُۥ لَمَجۡنُونٞ
English translation: And indeed would almost those who disbelieve surely make you slip with their eyes when they hear the Message and they say Indeed he (is) surely mad
Transliteration: wa-in yakadu alladhina kafaru layuz'liqunaka bi-absarihim lamma sami'u al-dhik'ra wayaquluna innahu lamajnunun