The "minor prophet" Joel prophesied Pentecost in vivid language to a sinful people in desperate need of hope for salvation. People just like us, before Jesus.
Junk has a way of piling up in your heart just like it does in your home...especially if you're not vigilant. For awhile you can keep your eyes on the clean spaces. But eventually there is nowhere else to look; that's when it's time for a little soul cleaning.