Joel’s message is this: the day of the Lord is coming, so we must warn people and call them to repentance and faith before it is too late! He uses a past incident of judgment and a locust infestation to cast a vision for future judgment. He issues a call to hear the word of the Lord and tell the next generation.
The theme of Joel is, “The Day of the Lord.” The phrase occurs 12 times total throughout the books of the minor prophets and five times in the book of Joel alone. Joel prophesies the day of Pentecost, when the Holy Spirit would be poured out on the new converts in the early church.