Albert Barnes on Acts 23:17

Called one of the centurions. Who might at that time have had special charge of the castle, or been on guard. Paul had the most positive assurance that his life would be spared, and that he would yet see Rome; but he always understood the Divine promises and purposes as being consistent with his own efforts, and with all proper measures of prudence and diligence in securing his own safety. He did not rest merely on the Divine promise without any effort of his own; but he took encouragement from those promises to put forth his own exertions for security and for salvation.

(b) "Paul called" Prov 22:3, Mt 10:16 (*) "chief captain" "commander"