If Allah hates injustice and evil, why doesn’t He punish it immediately? Why the delay? Doesn’t this encourage people to do more bad deeds?  

This question can be answered on two levels. The first level is that when Allah punishes a sin to its full extent in this world, it is an act of mercy for punishment in the next world is much, much worse. If a person fails to see much of a punishment vetted out against him or her in this life, you know that he or she is in real trouble.  

The second level is that all sins are punished in this world. What we call delay is a delay in “full punishment”. 

People are punished in this world for all the misdeeds they do. First, the punishment comes through the pollution and darkening of one’s soul. Second, God is often subtle in His punishments where it comes to us in ways we don’t expect or notice.