How do we reconcile God's forgiveness of sins with His attribute of justice?

There is no contradiction between God's justice and His forgiveness of sins. Forgiveness is a favor from Him, and if He, Glorified be He, were to punish the inhabitants of His heavens and His earth, He would not be unjust to them. And if He were to show them mercy, His mercy would be better for them than their deeds. As for the Mutazilites' assertion that if God punishes one, He punishes all, and if He forgives one, He forgives all, and their view that forgiving some but not others is injustice, this is false both rationally and textually. Rationally: A king is not considered unjust if he punishes one wrongdoer and overlooks another. Textually: Allah Almighty says: (He forgives whom He wills and punishes whom He wills), and (He punishes whom He wills and has mercy on whom He wills), and (He is not questioned concerning what He does, but they will be questioned). Indeed, God is the Ruling Disposer who does what He wills and decrees what He desires, and His justice does not wrong an atom's weight.