Peter says it all...

The disciples must have been stunned, filled with joy and excitement that first Easter Sunday. Yet that was only a start ... their new lives had barely just begun, and so they waited around in Jerusalem after Jesus had returned to heaven. Then the Holy Spirit came and everything changed. This was the end, and yet the beginning, of the story of Jesus's life on earth. Peter, the illiterate fisherman, who until then seemed to have more faults and failings than admirable qualities, became an eloquent and impassioned orator:

"Jesus the Nazarene, a man thoroughly accredited by God to you—the miracles and wonders and signs that God did through him are common knowledge—this Jesus, following the deliberate and well-thought-out plan of God, was betrayed by men who took the law into their own hands, and was handed over to you. And you pinned him to a cross and killed him. But God untied the death ropes and raised him up. Death was no match for him. David said it all:

I saw God before me for all time.
Nothing can shake me; he's right by my side.
I'm glad from the inside out, ecstatic;
I've pitched my tent in the land of hope.
I know you'll never dump me in Hades;
I'll never even smell the stench of death.
You've got my feet on the life-path,
with your face shining sun-joy all around.

"Dear friends, let me be completely frank with you. Our ancestor David is dead and buried—his tomb is in plain sight today. But being also a prophet and knowing that God had solemnly sworn that a descendant of his would rule his kingdom, seeing far ahead, he talked of the resurrection of the Messiah—'no trip to Hades, no stench of death.' This Jesus, God raised up. And every one of us here is a witness to it. Then, raised to the heights at the right hand of God and receiving the promise of the Holy Spirit from the Father, he poured out the Spirit he had just received. That is what you see and hear. For David himself did not ascend to heaven, but he did say,

God said to my Master, "Sit at my right hand
Until I make your enemies a stool for resting your feet."
"All Israel, then, know this: There's no longer room for doubt—God made him Master and Messiah, this Jesus whom you killed on a cross."

Cut to the quick, those who were there listening asked Peter and the other apostles, "Brothers! Brothers! So now what do we do?"

Peter said, "Change your life. Turn to God and be baptized, each of you, in the name of Jesus Christ, so your sins are forgiven. Receive the gift of the Holy Spirit. The promise is targeted to you and your children, but also to all who are far away—whomever, in fact, our Master God invites."

He went on in this vein for a long time, urging them over and over, "Get out while you can; get out of this sick and stupid culture!"

Acts 2:22 - 40, The Message

Many of Peter's listeners did just that: they started off on a new life with Christ. The rest is history...