God promises a great outpouring of his Spirit

Joel 2:18-32
Be glad, O people of Zion, rejoice in the Lord your God, for he has given you the autumn rains in righteousness. You will have plenty to eat, until you are full, and you will praise the name of the Lord your God, who has worked wonders for you.
Then you will know that I am in Israel that I am the Lord your God, and that there is no other; never again will my people be shamed.
And afterward, I will pour out my Spirit on all people. Your sons and daughters will prophesy, your old men will dream dreams, your young men will see visions.
Before the coming of the great and dreadful day of the Lord. Everyone who calls on the name of the Lord will be saved.
Moved with pity and compassion, God promises to restore in profusion all that the locusts have taken. He will rid the land of the locust army he has sent against them.
More than this, God promises a great outpouring of his Spirit, not just on priests and prophets, but on ordinary people, regardless of gender, age, or class.
Why?
High point: rejoice in the Lord your God, who has worked wonders for you.
Spot point: God's spirit will pour out on his people, not only priests.
Main point: The salvation messages has been sent to all people, but repent and pray to Him.
Peter, addressing a crowd of Jews gathered in Jerusalem from 'every nation under heaven', announces that this prophecy of Joel is being fulfilled.
Northerner: Locust hordes generally invade Palestine from the south or east. The military threat, however, was from the north. So northerner here may indicate a hostile enemy, rather than saying where the locusts came from.
How?
God's mercy and salvation with Holy Spirit pour upon not only priests but his people, who loves God and calls on name of the Lord.