John Gill Commentary Acts 26:1

"And Agrippa said unto Paul, Thou art permitted to speak for thyself. Then Paul stretched forth his hand, and made his defence:" — Acts 26:1 (ASV)

Then Agrippa said to Paul
After Festus had made the above speech to him, and to all present, and had introduced the affair of Paul, who now stood before them.

you are permitted to speak for yourself ;
which a prisoner might not do, until he had leave; and this leave was granted by Festus the Roman governor, who was properly the judge, and not Agrippa, though the permission might be by both; and so the Arabic and Ethiopic versions read, "we have ordered", or "permitted you".

Then Paul stretched forth the hand ;
as orators used to do, when they were about to speak; or else to require silence; or it may be to show the freedom of his mind, and how ready he was to embrace the opportunity of pleading his own cause; being conscious to himself of his innocence, and relying on the ingenuity and integrity of his judge; and especially of the king, before whom he stood.

and answered for himself ;
or made an apology, or spoke in vindication of himself, in order to remove the charges brought against him.