Jesus told His disciples to wait for the empowering of the Holy Spirit before they began their open ministry. This passage begins with that empowerment.
Then Peter (dubbed the big fisherman) began to speak. He was always the most enthusiastic by nature. Whatever he did, he did all the way. No half measures for Peter.
But look at his discourse. He quotes the prophet Joel word for word. Then he speaks the words of David from Psalm 16 and again from Psalm 110.
As a public speaker, I know how difficult it is to remember verbatim as you speak. Your mind jumbles with a million details. You work to concentrate on what you are saying and the order in which you are saying it. When speaking to a group, I spend much time beforehand preparing what I'm going to say, rearranging the order, adding or subtracting small details. Then I practice several times to make sure I can do it in the time frame allotted.
Peter had an advantage. He didn't have to do a twenty-minute keynote after dinner. He had an open time frame. But he had the biggest advantage of all with the Holy Spirit poured out upon him.
You see, God knows all He wants to say to you. And being perfect, He says it perfectly. That's why Peter, an unschooled fisherman, was able in the power of the Holy Spirit to speak this moving testimony, quoting the prophet and the psalmist.
When you are sensitive to the indwelling Spirit of God within you, He can use you to speak His words, in His timing, to His chosen audience.
Would that we all were such hearers and speakers.
Grant us the wisdom to put self aside and listen only to the promptings of Your Holy Spirit. Let us speak the words of comfort or conviction that You would have us speak. Bridle our tongues to Your use alone.
In Jesus' most precious name.