But you will receive power when the Holy Spirit has come upon you. You will be witnesses to me in Jerusalem, in all Judea and Samaria, and to the uttermost parts of the earth."

This Jesus God raised up, to which we all are witnesses.

We are witnesses of everything he did both in the country of the Jews, and in Jerusalem; whom they also killed, hanging him on a tree.

and he was seen for many days by those who came up with him from Galilee to Jerusalem, who are his witnesses to the people.

and that repentance and remission of sins should be preached in his name to all the nations, beginning at Jerusalem.

You will also testify, because you have been with me from the beginning.

This is the third time I am coming to you. "At the mouth of two or three witnesses shall every word be established."

how will we escape if we neglect so great a salvation -- which at the first having been spoken through the Lord, was confirmed to us by those who heard;

And so

"When the Counselor has come, whom I will send to you from the Father, the Spirit of truth, who proceeds from the Father, he will testify about me.

Nevertheless I tell you the truth: It is to your advantage that I go away, for if I don't go away, the Counselor won't come to you. But if I go, I will send him to you.

God also testifying with them, both by signs and wonders, by various works of power, and by gifts of the Holy Spirit, according to his own will?

To them it was revealed, that not to themselves, but to you, they ministered these things, which now have been announced to you through those who preached the Good News to you by the Holy Spirit sent out from heaven; which things angels desire to look into.

Whom

They were all filled with the Holy Spirit, and began to speak with other languages, as the Spirit gave them the ability to speak.

While Peter was still speaking these words, the Holy Spirit fell on all those who heard the word.

But he said this about the Spirit, which those believing in him were to receive. For the Holy Spirit was not yet given, because Jesus wasn't yet glorified.

General references

When they bring you before the synagogues, the rulers, and the authorities, don't be anxious how or what you will answer, or what you will say;

You are witnesses of these things.