Sometimes the book of Job is discussed under the heading, "The problem of suffering." But the book does not really answer why we suffer. It does teach us that faith in God, and dependence upon Him, makes suffering endurable, hopeful, and thus manageable.
After all the accusations and counter claims in the book, after all God's discourses with Job, Job never learned the reason for his suffering. He continued to serve God and died without knowing. But he learned to trust God who has answers we don't understand.
But we know why Job suffered. Satan had accused man, saying in essence, "Every man has his price." Thus God had Job stand in our place and prove the nobility and principled behavior (as opposed to mere opportunism or pragmatism) of which man is capable. Because of who God is, good men will endure the utmost suffering to serve God out of mere faith and love.
As Christ stood in our place, so did Job. And both suffered for precisely the same reason. They were righteous. An unrighteous person could not have successfully endured, represented, and performed what was best in, and for, man. Job's accusers argued that his suffering was a sign of his unrighteousness. But the suffering of neither Christ nor Job had anything to do with their own sins. That is why Job foresaw Christ as his redeemer (vindicator, Job 19:25 ). Suffering does not necessarily denote God's displeasure with a particular individual. And regardless of the terrible anguish in Job's life during the events of the book, we can be sure Job is now rejoicing because of his role in the history of man, and rejoices at the suffering he endured, knowing now the crushing blow it was to Satan, and the glory it gave to God.
The vicarious suffering of neither Christ nor Job needs repetition. Once the ability of humans to act with integrity was proved, and once atonement was made, it was not necessary to establish or accomplish either again. It was done.
A problem some have had with the book is this: If it is to prove the nobility of man, doesn't the convenient and romantic ending where Job is rewarded, detract from pure nobility? Job was given even greater substance and standing than before. The answer is that the ending completes his typifying Christ, who would be exalted and glorified after his suffering (Heb. 12:3; Phil. 2:5-11).
The answer as to why there is suffering in a sinful world ruled by a good God, is found elsewhere. If this realm where sin abounds, were suffering-free, man would be content and never yearn for better. He would continue in sin and never seek God. So God subjected this place to vanity, "in hope" that man would seek deliverance from this bondage of sin and find the eternal life available to him in God's plan (Rom. 8:18 -25). In a world that suffers, God produces the craving of hope. And suffering declares that God's order, as it had been in Eden , cannot be corrupted without consequences. There are consequences in a world of sin. Sin is here, and the creation suffers, even those who have the firstfruits of the Spirit. This is not our abiding place; this is not for what we were made. Job stood in our place and proved the nobility and faith of which man is capable. Christ stood in our place and atoned for our sins. The hope is attainable. -- Dale Smelser