You are reading a tafsir for the group of verses 21:16 to 21:18

Those who are not serious about the divine call, consider the present world as a plaything of God which has no purpose except temporal entertainment. But judging by the immense wisdom and meaningfulness underlying the working of the present world, it would appear to be impossible that the Creator of this world could be a being who has created it merely for the sake of diversion. In the present world, there is the special creation of God, namely, human beings, who by their very nature, have the ability to distinguish truth from falsehood. The existence in the world of such creatures, who can use their discretion and decide upon one path as that of truth and another as that of untruth, coupled with the frequent struggle between Truth and untruth, are all indications of the fact that a time is going to come when it will finally be clear as to what is really Truth and what is Untruth. And whoever sides with the Truth will attain success and whoever does not will be doomed to failure.