In Gen. i. and ii. we have the creation of man. In Gen. iii. we have the fall of man, and the chapter ends with the statement that man was driven out from the Garden of Eden in judgment (v. 24). Then, in Gen. iv., what have we but the way back again to God, in grace? God's way, which Abel took; and man's way, which Cain invented.
This, therefore, is the oldest lesson in the world. It is the first great lesson which stands on the fore-front of revelation; and the lesson of the book of Job follows this up and expands it by answering the solemn question, "How should man be just with God?"
This is not only the oldest lesson, but it is the most important lesson that it is possible for us to learn. If we know not this lesson, it matters not what else we may know. Our knowledge may be vast, extensive, and deep on all other subjects; but it will not carry us beyond the grave.
But the knowledge of this lesson will serve us for eternity; and secure our eternal blessing and happiness. If we know this lesson, it matters little what else we do not know.
No wonder then that this oldest lesson in the world is thus set at the very opening of God's Word, following immediately upon the record of the Fall. No wonder that, thus, at the threshold of the Word of God, we have the foundation of Gospel truth securely laid.
The "end" which the Lord had in view in the book of Job was to enforce this lesson in the most powerful way; a way which should serve as an object lesson for all time; and by the manner in which it is set forth should impress its importance upon the hearts and minds of all.
from page 2- 3, The Book of Job