Little is known about the prophet Joel, although his concern for Judah and Jerusalem suggests that he ministered in Judah. Joel told of a locust plague that had struck Israel and which, he said, foreshadowed the "day of the Lord." The day of the Lord was a time greatly anticipated by the Israelites because they believed that God would then judge the nations and restore Israel to her former glory. Yet, said Joel, God would punish not only the nations but unfaithful Israel as well. Joel urged everyone to repent, and told of a day when God would "pour out [his] Spirit on all flesh" (2:28). That day arrived on the first Christian Pentecost (Acts 2:17). While the date of the book is uncertain (ninth to sixth century b.c.), its message is valid for all time.