John Gill Commentary Acts 26:6

"And now I stand [here] to be judged for the hope of the promise made of God unto our fathers;" — Acts 26:6 (ASV)

And now I stand, and am judged
Before the Roman governor, and in the presence of Agrippa:

for the hope of the promise made of God unto our fathers ;
either for the hope of righteousness, life, and salvation, by the Messiah; who was promised to the Jewish fathers, Abraham, Isaac, and Jacob, and others; see (Genesis 22:18) (49:10) or for the hope of the resurrection of the dead, and eternal life; of which there are various testimonies in the writings of the Old Testament, committed to the people of the Jews. (Job 19:26Job 19:27) (Isaiah 26:19) (Daniel 12:2) and others.

And both these senses may be very well joined together, for it was for asserting that the promised Messiah was come, and that Jesus of Nazareth was he; that he was risen from the dead, and that all the dead will be raised by him; and that life and righteousness, salvation, and everlasting glory and happiness, are only by him; for asserting these things, I say, the apostle was now a prisoner, and stood at the bar of a Roman judge, being accused by the Jews.