Joel was a prophet whose short book calls people to return to God with all their heart, and famously promises the day when God would pour out his Spirit on all flesh — words Peter quoted at Pentecost.
Timeless and popular, Joel is a name that is itself a confession: the LORD is God.
Joel in the Bible
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: