Allah is Much-forgiving, Merciful. Wrongdoing is an action which is both positive and evil. Therefore, it is not sufficient that a wrongdoer stops doing what is wrong. He should go further than that and do something which is both positive and good. In Islamic law, however, the matter goes further than that.
Man is a creature who has to have something to do.
If he stops doing evil without moving on to do good, he feels himself to be in a vacuum which may turn him back toward evil. But when he is positive and does good action, then he moves far from evil. This is an important aspect of the Islamic method of educating people and cultivating goodness in them. Finally, the surah states the overall principle of punishment in this life and in the hereafter. Allah, the Creator and Owner of the universe, can 'will' anything and determine the fate of every creature.