The book names Joel
The opening verse gives the clearest answer available. It says that the word of the Lord came to Joel, son of Pethuel (Joel 1:1). In other words, Joel is the prophet through whom God gave the message recorded in this book.
The Bible does not tell us much more about him. Pethuel, Joel’s father, is named, but no other biblical passage fills in Joel’s family background, occupation, age, or the beginning of his prophetic calling. That can feel brief, but it suits the book’s purpose. Its focus is not on Joel’s story, but on God’s word.
The word of the Lord that came to Joel the son of Pethuel.
A prophet sent to Judah
Joel’s message was addressed to God’s covenant people, with special attention to worship in Judah. He calls priests to mourn and serve in the house of God, and he calls the whole community to gather before the Lord during a devastating crisis in the land (Joel 1:13-14). He also speaks of sounding an alarm in Zion, the place closely connected with God’s people and worship (Joel 2:1).
So Joel was not writing abstract religious thoughts. He was speaking into a real national emergency, urging people to seek God together. His words address elders, farmers, priests, children, and the wider assembly (Joel 1:2; Joel 1:11; Joel 2:16).
His message included warning and hope
Joel warns that the day of the Lord is serious, but he does not leave people without hope. He calls them to return to God with their whole heart, and he points to God’s gracious and merciful character (Joel 2:12-13). That invitation lies near the centre of the book.
The prophecy also looks beyond the immediate crisis. Joel speaks of God pouring out his Spirit on all kinds of people, including sons and daughters, old and young, servants and handmaids (Joel 2:28-29). Later, Peter referred to these words when he explained what was happening at Pentecost (Acts 2:16-18).
Therefore also now, saith the Lord, turn ye even to me with all your heart, and with fasting, and with weeping, and with mourning: And rend your heart, and not your garments, and turn unto the Lord your God: for he is gracious and merciful, slow to anger, and of great kindness, and repenteth him of the evil.
What remains unknown
Christians and scholars have proposed different dates for Joel’s ministry. The book does not name a reigning king, as several other prophetic books do, so its exact setting is difficult to establish from Scripture alone. It does, however, clearly locate the message among God’s people, referring to Zion and Jerusalem (Joel 2:32).
The careful answer, then, is simple. Joel, son of Pethuel, was the human author or messenger named by the book itself. We need not invent details Scripture does not give. What Joel does make clear is God’s call to return to him, his promise of mercy, and his power to save those who call on his name (Joel 2:32).
And it shall come to pass afterward, that I will pour out my spirit upon all flesh; and your sons and your daughters shall prophesy, your old men shall dream dreams, your young men shall see visions: And also upon the servants and upon the handmaids in those days will I pour out my spirit.