Mark 16:9-20; Acts 1:1-11; Acts 1:12-2:47

The Bible's book of Acts, chapter 2, describes the fulfillment of a prophecy recorded in the Bible's book of Joel, chapter 2, verses 28-32. According to Peter the Apostle's understanding, as reported in Acts 2, the Spirit of God is poured into the disciples of Jesus who are obediently waiting. 

Choirstall woodcarving of the Pentecost, with tongues of fire descending upon the apostles, detail, from Art in the Christian Tradition, a project of the Vanderbilt Divinity Library, Nashville, TN. http://diglib.library.vanderbilt.edu/act-imagelink.pl?RC=51555 [retrieved November 11, 2015]. Original source: Collection of Anne Richardson Womack.

But the prophecy found in the Bible's book of Joel indicates that God will pour Spirit into all people and that everyone who calls on the Lord's name will be saved. I suppose that this outpouring must begin with someone, somewhere. And given what happens next--the addition of thousands to the movement (Acts 2:41)--it appears to be a fruitful start for the Spirit's activity in and among humankind.