The day of the LORD that Joel warned about was an armed invasion. The various images he used conveyed the idea of a sudden overwhelming presence. It would be sudden, like the appearance of a charging horse. They would violently break into the houses like a thief. Joel charged his listeners to pray and fast now, not to wait for signs of the approaching army. The sign was the prophecy itself. That is the way of the next day of the LORD as well. When Jesus appears, it will be too late to prepare for him. Are you ready?
LORD, make us ready for your day.
Joel 2:1-17