[Verse-by-Verse Comments, continued]
14But Peter, standing with the eleven, raised his voice and addressed them, “Men of Judea and all who live in Jerusalem, let this be known to you, and listen to what I say.
(1) This demonstrates the power of the Holy Spirit. Just seven-plus weeks before, Peter denied even knowing Jesus. Now, in spite of the implicit danger of being associated with Jesus, Who was executed, Peter stands up to give witness to his faith in Christ.
15Indeed, these are not drunk, as you suppose, for it is only nine o”clock in the morning.
(1) Peter evidences having done the very first thing any witness for Christ must do. He listened. His words come in response to the questions and accusations of the crowd in Jerusalem.
(2) Peter is arguing that it's way too early for all these people to be drunk; the taverns aren't even open yet!
16No, this is what was spoken through the prophet Joel: 17‘In the last days it will be, God declares, that I will pour out my Spirit upon all flesh, and your sons and your daughters shall prophesy, and your young men shall see visions, and your old men shall dream dreams. 18Even upon my slaves, both men and women, in those days I will pour out my Spirit; and they shall prophesy. 19And I will show portents in the heaven above and signs on the earth below, blood, and fire, and smoky mist. 20The sun shall be turned to darkness and the moon to blood, before the coming of the Lord’s great and glorious day.
(1) Another thing a witness for Christ must do is connect God's story with my story and your story. By knowing the Bible, Peter knows God's story.
(2) Peter is saying that there is a different explanation for this strange phenomenon. Simply, God's Holy Spirit has come to Jesus' believers, empowering them to witness for Christ.
(3) To prophesy, in Biblical terms, is to share God's truth.
21Then everyone who calls on the name of the Lord shall be saved.’
(1) In its way, this passage, lifted from the Old Testament prophet Joel, is "the Gospel in a nutshell." Gospel is the Old English translation of the New Testament Greek term, evangel, meaning good news. Christians have good news to share: God is for the human race. All who seek help and forgiveness from the God we meet in Jesus Christ will be saved from sin and death and have fellowship with God forever.