Word by Word Analysis

وَإِن يَكَادُ ٱلَّذِينَ كَفَرُوا۟ لَيُزْلِقُونَكَ بِأَبْصَـٰرِهِمْ لَمَّا سَمِعُوا۟ ٱلذِّكْرَ وَيَقُولُونَ إِنَّهُۥ لَمَجْنُونٌ 51

And indeed, those who disbelieve would almost make you slip with their eyes [i.e., looks] when they hear the message, and they say, "Indeed, he is mad."