The Spirit poured out at Pentecost
At Pentecost, Peter said that the outpouring of the Holy Spirit was what Joel had spoken, then quoted Joel's promise that God would pour out His Spirit on all people.
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. Even on My menservants and maidservants, I will pour out My Spirit in those days. I will show wonders in the heavens and on the earth, blood and fire and columns of smoke.
Joel 2:28-32 promises the outpouring of God's Spirit; Acts 2:16-21 introduces the same words by naming the prophet Joel and quotes the passage.