Allah is Just. In XCV:8, the Quraan says "Is not Allah the most conclusive of all judges?"
Again in XXI:47 "And we have provided a Just balance for the Day of Judgement. No soul shall be dealt with unjustly in any way. (Any good deed or evil deed) though it be as small as a grain of the mustard seed, will be brought forth by Us (in testimony). We suffice as the best of reckoners."
The Sunni School of thought subscribes to the view that nothing is good or evil per se. What God commanded us to do became good by virtue of His command. What he forbade became evil.
The Shias believe that there is intrinsic good or evil in things. God commanded us to do the good things and forbade the evil. God acts according to a purpose or design. Human reason cannot comprehend this design or purpose in its entirety though man must always strive to understand as much as he can.