Some Notes on Biblical Prophecy

"I consider it a sin to talk about prophecy without including hope." So said Ron Dart in a sermon he gave on 10-10-98, titled 'Why Prophecy?'
No prophecy is unchangeable and while some negative and fearful prophecies in the Bible seem destined to occur as written, such is not always the case.
Consider the dire message God gave Jonah to deliver to the people of Nineveh?  God commanded His prophet Jonah to cry out to the people of Nineveh, "Yet forty days and Nineveh shall be overthrown."
Let's consider what happened. Did Jonah obey God and warn the people of Nineveh that God would destroy this great city-state in 40 days if it did not repent? Yes. Was this a true prophecy? Yes. Did it come to pass? No. Why not? Simply because the people of Nineveh heeded the warning and repented. From the least to the greatest.
As a result, God changed His mind and allowed the people to live. He 'repented' of His decision to destroy the vast city and everyone in it.
See an example of where God again changed His mind and did not destroy another people He came close to wiping out because of their idolatry (Ex. 32:14).
Did God know what the outcome would be? Hardly. If the future had already been set, then the people of Nineveh would have had no choice and God would have known how they would have reacted to Jonah's warning in advance. The whole exercise would have been pointless
Notice Jonah's incredible reaction to God's mercy in not carrying through His intention to destroy Nineveh. He was 'exceedingly displeased, and it kindled anger in him (Jonah 4:1). Wow. Listen to his reasoning. 'And he prayed to the Lord and said, "Please, O Lord, was this not my saying when I was still in my land? Therefore on account of this I fled to Tarshish, for I knew that You are a gracious God, and merciful, slow to anger, and of great kindness, and One who repents of the evil" (v.2). Jonah tried to avoid carrying out his assignment not so much because he was fearful of the response from the people of Nineveh but because he knew there was a good chance that God would not destroy its' inhabitants. Nineveh was a very warlike city-state that had done great damage to Israel and so, Jonah wanted the city totally destroyed. It was a totally understandable desire (but not a godly one) and when it did not happen, he said to God, "And now, O Lord, I beseech You, take my life from me, for better is my death than my life" (v. 3). That is the reason why Jonah is called 'the reluctant prophet'.
A good insight on the message of Jonah's mission is explained in this article.