“But God raised him from the dead, and he was seen for many days by those who came up with him from Galilee to Jerusalem, who are now his witnesses to the people.”
But that was not the end, for God raised Him (egeiren) from the dead, just as he had ‘raised up David' (egeiren - Acts 13:22), so that He was seen of many witnesses. He had ‘raised up David' when he had been almost under sentence of death, delivering him and keeping him for when He would appoint him king. And He had done the same for Jesus. But this time the sentence of death had been allowed to be carried out, and he had then revealed man's folly by counteracting it, and even more, by exalting the One Whom He had raised, just as the prophets had said (Isaiah 52:13; Daniel 7:13-14)). Again God was bearing witness to the Greater David Whom He had sent. And these witnesses were not men of Jerusalem, but men of Galilee, those who had come up with Him to Jerusalem.
Having thus declared the resurrection, and emphasised the many witnesses, he now seeks to demonstrate it from the Scriptures. For as he has previously said, the Scriptures too are witnesses (Acts 13:27; Acts 13:29).
Anyone purporting to be Paul and seeking to imagine what he might have said, would have introduced the account of Paul's own vision of the risen Jesus here as evidence for the resurrection. But Paul himself recognised that that experience had been unique and personal, not something to be openly spoke of in order to provide a witness for the resurrection.