"The Bible was clearly written either by God, good men, or bad men. Bad men could not have written it, for the Bible is a good book, and fresh waters do not come from a salt fountain; bad men would not have written it, for the Bible strongly condemns sin and sinners, and wicked men would not condemn themselves to hell. Good men could not have written it, and then deliberately said God wrote it: they would no longer be good men; good men would not have written it for the definite purpose of deception, for good men do not decieve. Hence, the only one left who could have written it is God."
Taken from A Firm Foundation by Dr. David H. Peterson