The Gourd teaches Jonah a lesson in mercy.
The book of Jonah can be summed up in one word, "mercy."
The story reveals the truth about a merciful God who does not desire the death of a sinner but rather that the sinner turn away from evil toward the good.
The prophet Jonah knows that God is a God of mercy. God's disposition toward mercy is the reason that, in the first place, caused Jonah to run away.
He did not want to waste his effort preaching to a gentile people because he knew that if they were to repent and turn away from an evil life then God would forgive them.
Jonah has a double fault here.
Firstly, he is a "saved" person of the light who does not care that other people also get to the light.
Secondly, he is annoyed at the idea that it is his responsibility as a person of the "light" to work toward bringing others into the light of God.
Jonah has a difficult time embracing the idea of God's goodness. It seems that Jonah does not want a god of mercy but a God of justice. Even more, the god of justice that Jonah seems to want is a god whose justice is without mercy.
In the story of the Gourd, Jonah is shown to care more about his own comfort than he does about the welfare of a whole city. The fault here is one of personal selfishness.
The story also points to another fault. Jonah is one of the Chosen people. They were chosen for the purpose of revealing to the world the true knowledge concerning the one God. To the chosen people belonged the revelation from the only god who is really a God.
The history of the chosen people as told in the Bible is the story of their experience with this one true God. It tells of God's creation of, care for and continued relevation to the Chosen people.
The uncovering of the hidden truths about God were revealed to the chosen people not in order for them to be proud, careless or callous. Rather, God's intention in selecting the Hebrew tribe to become the Israelite nation was in order to underscore and highlight the graciousness of God.
The small band of Abraham that grows into the collection of people known as the twelve tribes and eventually after their sojourn in Egypt becomes a nation of six hundred thousand...this development is the story of how God takes a people of no account and creates through them a great people.
However, the greatness of the people is for the purpose of being a blessing to all the nations of the world. The chosen people who had the light of God revealed to them on Mount Sinai, are to be (themselves) a light to give revelation about God to the rest of the world.
What is shown to us in the story of the Gourd is an arrogance on the part of the chosen over against other peoples and nations. Instead of bringing to others salvation, the chosen can fall into the mistake of pride which regards themselves as superior to those around them
Thus we see that personal selfishness and mis placed religious pride are not what God intends for the world. Rather, God intends mercy.