Key Verses

1. 9:45At-TawbahWarning
   إِنَّمَا يَسۡتَـٔۡذِنُكَ ٱلَّذِينَ لَا يُؤۡمِنُونَ بِٱللَّهِ وَٱلۡيَوۡمِ ٱلۡأٓخِرِ وَٱرۡتَابَتۡ قُلُوبُهُمۡ فَهُمۡ فِي رَيۡبِهِمۡ 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.
   In context

   Those who ask the Messenger (peace be upon him)for permission to stay behind from striving for the sake of Allah are the hypocrites who do not believe in Allah and the Day of Judgement, and whose hearts are full of doubt about the sacred path of Allah. In their doubt they waver, confused, and they are not guided to the truth.