I (God) make you rich and poor, happy and sad, sick and healthy, blind and visible, able and disable is not to believe me (God) but to REALIZE me (God)

Because you cannot believe me while sinning

I (God) neither reward nor punish you 

You punish yourself from bad actions or free you from good actions because it is your free will

I am (God) the most merciful

If you fail to REALIZE ME (God) you will be caught in my Karma cycle which would follow you until you REALIZE ME (God)

If you fail to REALIZE me (God) 
You will be blind on earth as well in the hereafter – Quran 17.72