Acts 26
26 Then Agrippa said to Paul, “You are permitted to speak for yourself.”

So Paul stretched out his hand and answered for himself: 2 “I think myself happy, King Agrippa, because today I shall answer for myself before you concerning all the things of which I am accused by the Jews, 3 especially because you are expert in all customs and questions which have to do with the Jews. Therefore I beg you to hear me patiently.

4 “My manner of life from my youth, which was spent from the beginning among my own nation at Jerusalem, all the Jews know. 5 They knew me from the first, if they were willing to testify, that according to the strictest sect of our religion I lived a Pharisee. 6 And now I stand and am judged for the hope of the promise made by God to our fathers. 7 To this promise our twelve tribes, earnestly serving God night and day, hope to attain. For this hope’s sake, King Agrippa, I am accused by the Jews. 8 Why should it be thought incredible by you that God raises the dead?

Paul then starts with a little background information. Everyone knows who I am. I grew up and lived a Pharisee.
Then he argue his main point, “why should you think God raising the dead as crazy?”

Here is verse 8 in “the message”
For the life of me, I can’t see why it’s a criminal offense to believe that God raises the dead.

Paul’s biggest argument, was that Jesus was raised from the dead for our sins.  For this, Paul is being persecuted.

9 “Indeed, I myself thought I must do many things [a]contrary to the name of Jesus of Nazareth. 10 This I also did in Jerusalem, and many of the saints I shut up in prison, having received authority from the chief priests; and when they were put to death, I cast my vote against them. 11 And I punished them often in every synagogue and compelled them to blaspheme; and being exceedingly enraged against them, I persecuted them even to foreign cities.

I think “the message” explains this one rather well also:
9-11 “I admit that I didn’t always hold to this position. For a time I thought it was my duty to oppose this Jesus of Nazareth with all my might.

Paul is trying to explain that he can relate to their hatred of Jesus of Nazareth, because he too felt it when persecuting believers of “the Way.”