﴿ إِنَّمَا يَسْتَـْٔذِنُكَ ٱلَّذِينَ لَا يُؤْمِنُونَ بِٱللَّهِ وَٱلْيَوْمِ ٱلْءَاخِرِ وَٱرْتَابَتْ قُلُوبُهُمْ فَهُمْ فِى رَيْبِهِمْ يَتَرَدَّدُونَ ﴾

“only those ask thee for exemption who do not [truly] believe in God and the Last Day and whose hearts have become a prey to doubt, so that in their doubting they waver between one thing and another.”

(They alone ask leave of you) to stay behind and not take part in jihad (who believe not in Allah and the Last Day) in the depth of their hearts, (and whose hearts feel doubt, so in their doubt they waver) they are bewildered.