A.T. Robertson Commentary Acts 23:18

"So he took him, and brought him to the chief captain, and saith, Paul the prisoner called me unto him, and asked me to bring this young man unto thee, who hath something to say to thee." — Acts 23:18 (ASV)

Paul the prisoner (ο δεσμιος Παυλος). Bound (δεσμιος) to a soldier, but not with two chains (21:33), and with some freedom to see his friends as later (28:16), in military custody (custodia militaris). This was better than custodia publica (public custody), the common prison, but more confining.

Who hath something to say to thee (εχοντα τ λαλησα σο). Same idiom as in verse 17,19, but λαλησα here instead of απαγγειλα.