Qur'an 9:45

إِنَّمَا يَسْتَـْٔذِنُكَ ٱلَّذِينَ لَا يُؤْمِنُونَ بِٱللَّهِ وَٱلْيَوْمِ ٱلْـَٔاخِرِ وَٱرْتَابَتْ قُلُوبُهُمْ فَهُمْ فِى رَيْبِهِمْ يَتَرَدَّدُونَ

They alone ask leave of thee who believe not in Allah and the Last Day, and whose hearts feel doubt, so in their doubt they waver.