From Acts 2 with some notes -
When the Pentecost crowd heard [Peter's message] they were cut to the quick – “cut to the heart,” assailed by the conviction of the Holy Spirit – and they cried to Peter and the other apostles, “Men and fellow-Jews, what shall we do now?”
Peter told them, “You must repent – meaning, "alter the purpose of your life" – and every one of you must be baptized in the name of Jesus Christ – something never done before in human history – so that you may have your sins forgiven – a promise that Peter received directly from Jesus in Luke 24’s words, “So must the change of heart [the repentance] which leads to the forgiveness of sins be proclaimed in his name to all nations, beginning at Jerusalem” – and receive the gift of the Holy Spirit. For this great promise is for you and your children — yes, and for all who are far away, for as many as the Lord our God shall call to himself!”
To me, it’s fascinating just how boldly Peter proclaims “this great promise” – the receipt of “the gift of the Holy Spirit” for “all who are far away, for as many as the Lord our God shall call to himself” – when he himself had only just received this Holy Spirit! How could he know that these people would receive Him too? How could he be so bold as to promise them “this promise”?
We might assume that he was leaning upon the prophecy from Joel 2 – that the Spirit would be poured out “upon all flesh” – or that, in real time, he was remembering Jesus’ Holy Spirit teachings from John 14, 15 and 16.
Or maybe just maybe this former fisherman, this present vessel of the Holy Spirit of God, is now receiving his orders directly from the Throneroom of Heaven. Again, as Jesus had said: “Yet when that one I have spoken to you about comes — the Spirit of Truth — he will guide you into everything that is true. For he will not be speaking of his own accord but exactly as he hears, and he will inform you about what is to come.” And just as thrilling: “When they bring you before the synagogues and magistrates and authorities, don’t worry as to what defense you are going to put up or what word you are going to use. For the Holy Spirit will tell you at the time what is the right thing for you to say.” (Luke 12)
Just as surely as the Father and Son discuss their plans in the Holy Spirit’s hearing, so surely does the Holy Spirit hear and speak what He has heard to us; and so surely may we learn to hear and speak, just as He has heard and spoken, so that all men may know the Good News of Jesus.
Peter is not winging it in his Pentecost message. Peter is our first pattern for how we should learn to listen… and then speak.