Albert Barnes on Acts 21:33

To be bound with two chains. To show to the enraged multitude that he did not intend to rescue any one from justice, but to keep the peace. Paul's being thus bound would convince them of his determination that justice should be done in the case. Probably he was bound between two soldiers--his right arm to the left arm of the one, and his left arm to the right arm of the other. Acts 12:6. Or, if his hands and feet were bound, it is evident that it was so done that he was able still to walk, Acts 21:37,38. This was in accordance with the prediction of Agabus, Acts 21:11.

(*) "chief captain" "Commander" (b) "bound with two chains" Acts 21:11, 20:23, Eph 6:20