Jonah was distressed after his successful preaching led over 120,000 people in Nineveh to repent. God caused a plant to grow and then destroy it to remind Jonah that God is in control. The passage encourages examining one's priorities and whether one is more focused on trivial worldly things over the salvation of people's souls, as Jonah was more upset over the loss of a plant than the people of Nineveh turning to God.