Joel 2: 28-32 The promise of the Spirit:

"It will come about after this, that I will pour out My Spirit on all mankind, and your sons and daughters will prophesy, your old men will dream dreams, and young men will see visions. Even on the male and female servants, I will pour out My Spirit in those days. I will display wonders in the sky and on the earth such as blood, fire, and colomns of smoke. The sun will be turned into darkness, and the moon into blood before the great and awesome day of the Lord comes. And it will come about that whoever calls on the name of the Lord will be delivered; on Mount Zion and in Jerusalem, there will be those who escape, as the Lord has said, even among the survivors whom the Lord calls."

This is one of the great verses in the Old Testament with New Testament application. The giving of the Spirit is the Day of Pentecost whom Jesus said that he would send. The Spirit was sent to give the apostles and Christian's power. Starting on that day, those who called on Jesus as their Savior become indwelt by the Spirit of God, even to this very day. The awesome Day of the Lord is a reference to the latter days, the period of Great Tribulation before the second advent of Jesus.

Lord Jesus, I await your return which is the blessed hope. Hasten your return because the world and your redeemed groan until the day of our bodily redemption. In your name I pray Amen.