Acts 23:22
So the chief captain then let the young man depart, and charged him, See thou tell no man that thou hast shewed these things to me. So the chief captain then let the young man depart, and charged him, See thou tell no man that thou hast shewed these things to me.
The young man who carried the information was Paul's nephew. He came with a warning and a report of the plot laid against Paul, and after hearing it the chief captain let him go and dismissed him. The dismissal was accompanied by a strict charge to tell no one that he had shown these things and reported the plot to the commander. That order of secrecy was given so the captain could move forward without exposing his own plans.