There are some folks who think “the God of the Old Testament” is different than “the God of the New Testament.” They think that in the New Testament, God appears loving and compassionate while in the Old, He appears angry and vengeful.
Well, nothing could be further from the truth! God is the same in both. He has always been angry at sin but has also always been compassionate and willing to forgive an offense.
One such instance is found in the Old Testament book of Jonah. God told that reluctant prophet to go to Nineveh and warn the people in that city of the divine consequences of their sin.
After God made it clear that Jonah’s only response would be obedience, Jonah went. Yet, Jonah hoped that the citizens of Nineveh would not repent. He didn’t want them to experience God’s mercy. He wanted God to destroy them!
Why? Probably because he predicted that God would use those people to bring consequences upon his own rebellious people … the Israelites.
So, when Jonah warned the citizens of Nineveh of God’s impending judgment they repented, as Jonah feared. And, as Jonah expected, God compassionately relented of what He had threatened to do to them and did not bring devastating, divine consequences (Jonah 3:6-10).
How did Jonah respond? Was he overjoyed at a people who turned back to God? Was he as compassionate as “the God of the Old Testament”?
Jonah 4:1-3 (New Living Translation)
“This change of plans greatly upset Jonah, and he became very angry. So he complained to the LORD about it: ‘Didn’t I say before I left home that you would do this, LORD? That is why I ran away to Tarshish! I knew that you are a merciful and compassionate God, slow to get angry and filled with unfailing love. You are eager to turn back from destroying people. Just kill me now, LORD! I’d rather be dead than alive if what I predicted will not happen.'”

Anyone who thinks that “the God of the Old Testament” was a mean tyrant with a hard heart has obviously never read the Bible! God is infinitely more compassionate and forgiving than we are. Just look at the Cross!