Just like the man healed of Legion clung to Jesus (Mark 5:18)
12 And when Peter saw it he addressed the people: “Men of Israel, why do you wonder at this, or why do you stare at us, as though by our own power or piety we have made him walk?
This is one of my favorite statements of Peters in this sermon. He has by this time acquired the heavenly knack for saying impossibly absurd things as if they were ordinary. In fact this begins in earnest in Matt 14:31, when Jesus can't figure out why Peter would walk, and then stop walking on the water, "I don't get it, you were walking just fine a second ago." Or the angels rebuking him (Luke 24:5) for looking for the living among the dead. "Do you humans always walk around cemeteries looking for dead people? I simply don't understand your behavior" as if they don't recognize that they still thought He was dead. Or the other angelic rebuke Acts 1:11 "Why do you keep looking into the sky?" "Because that was incredible maybe?"
Why are you so astonished has the same feel to it. On the one hand, humanly speaking, it's amazing and beyond incredible. On the other hand, is it really any exertion of power for the God who made the universe to heal a man's legs?
13 The God of Abraham, the God of Isaac, and the God of Jacob, the God of our fathers,
Thus equating Jesus with the Ancient of Days
glorified his servant Jesus, whom you delivered over and denied in the presence of Pilate, when he had decided to release him.
Pilate may have been totally ruthless when it came to carrying out justice, but you had to say this about him: he wanted justice. He was cold and calculating in order to achieve an end of peace, rather than just bathe in blood like Herod the Great before him.
14 But you denied the Holy and Righteous One, and asked for a murderer to be granted to you,
you may think this was Barrabus, but this was actually me. And you.
15 and you killed the Author of life, whom God raised from the dead. To this we are witnesses. 16 And his name—by faith in his name—has made this man strong whom you see and know, and the faith that is through Jesus has given the man this perfect health in the presence of you all.
17 “And now, brothers, I know that you acted in ignorance, as did also your rulers.
This is why Jesus spoke in parables, so that hearing they may not hear, and seeing they may not see, lest they be hardened further. Should God have revealed Himself fully to them and they reject Him, there is no alternative. No escape, no forgiveness available. But since they acted in ignorance it is possible to come to Him, to ask for mercy. In other words, by keeping them blind and ignorant God has given them the gift of forgiveness. They can be saved should they take it.
18 But what God foretold by the mouth of all the prophets, that his Christ would suffer, he thus fulfilled.
Matthew 16:21, was a lesson Peter learned particularly well, considering Matt 16:23
19 Repent therefore, and turn again, that your sins may be blotted out, (our technical word is justified) 20 that times of refreshing may come from the presence of the Lord, (sanctified) and that he may send the Christ appointed for you, Jesus, (into our hearts that we may be adopted) 21 whom heaven must receive until the time for restoring all the things about which God spoke by the mouth of his holy prophets long ago.
22 Moses said, ‘The Lord God will raise up for you a prophet like me from your brothers. You shall listen to him in whatever he tells you. 23 And it shall be that every soul who does not listen to that prophet shall be destroyed from the people.’ 24 And all the prophets who have spoken, from Samuel and those who came after him, also proclaimed these days.
Luke 24:25-27. Christ is the sum and substance of the Old Testament. He is the One of whom it is written, and in Him all of it holds together. It points to Him, shows Him darkly, but nonetheless shows Him.
25 You are the sons of the prophets and of the covenant that God made with your fathers, saying to Abraham, ‘And in your offspring shall all the families of the earth be blessed.’
Because Abraham was blessed by His seed, which was Christ, a Jew must be in Christ to receive Abrahams blessing. In other words, the blessing of Abraham was Christ Himself and to turn away from Him is to forfeit your blessing as God's people. Thus Paul writes "they are not all Israel" and "a Jew is not one who outwardly." Without Christ there is no Abrahamic blessing, even if you have Abraham as your physical father.