The forceful rejection of the doctrine of mercy is voiced by a man who was willing to die rather than cause others to die, and who was willing to leave his native land and pay with his life rather than serve the compassionate God. His vigorous and sincere opposition to divine mercy is striking evidence that it is desperately needed. Just as the flight is unqualified, so is the pursuit relentless…
Jonah must bow his head before the absolute sovereignty of the divine will…before he can hear and understand the explanation given by God, who forgives without being lenient. The gates of escape are shut in the prophet’s face; precisely this provides the opening of the gates of repentance to the transgressors with its full significance, since both are direct outcomes of the Lord’s love for His creatures.
The paradoxical tension between the Lord’s inordinate severity with Jonah and His extraordinary leniency with Nineveh teaches us about the absolute sovereignty of the divine will; it is resolved only when Jonah comes to realize that the will of the Lord is not arbitrary, but compassionate, for those who are near and for those who are far from Him.
–from the JPS Bible Commentary on Jonah, by Dr. Uriel Simon