{ There is no blame on the blind, no blame on the lame, no blame on the sick. Whoever obeys Allah and His Messenger, He will admit him into gardens below which flow rivers, but whoever turns away, He will punish him painfully } Al-fath 17

This clarifies who is permitted to stay behind and abstain from jihad, and the reasons for which it is permissible to abstain from jihad, this being anything that prevents attacking and retreating, and this is made clear by stating three categories. The first is { the blind } , for indeed they can not attack or pursue the enemy, and they can not be on the lookout or flee. The lame are similar, as are the sick. Lameness implies those who are amputees or crippled; indeed that is even more reason for them to have an excuse. Those with a lameness that does not prevent them from attacking and retreating have no excuse, and similarly for those with light sickness that does not prevent attacking and retreating, such as disease of the spleen or a cough, if they are merely weakened by it; nor do certain joint pains constitute an excuse.