What does Acts 23:31 mean?

When Paul was traveling during the last few months of his third missionary journey, the Holy Spirit consistently told him that if he returned to Jerusalem, he would be arrested (Acts 20:22–23). Paul went anyway and the Roman army arrested him a few days after he arrived (Acts 21:33). Not long after, the Sanhedrin and forty other Jews conspired to have Paul killed (Acts 23:12–15). The Roman tribune, the military commander of the army barracks, heard of their plan and determined Paul would be safer with the governor (Acts 23:16–24).

Now Paul is riding to Caesarea Maritima, arrested but escorted by two hundred soldiers, seventy horsemen, two hundred spearmen, and two centurions to protect him from the Sanhedrin (Acts 23:12–15, 23). In Caesarea, he will stand trial before the governor, Felix, to determine if he committed a crime or if he's just squabbling about religious matters with the Sanhedrin (Acts 24:1–21).

The entourage leaves three hours after sunset (Acts 23:23) and stops at Antipatris. Antipatris is in Samaria, about thirty miles northwest of Jerusalem and twenty-eight miles south of Caesarea. Herod the Great built it and probably named it after his father, Antipater. From here, the soldiers and spearmen return to Jerusalem while the horsemen continue with Paul (Acts 23:32). The high priest Ananias, the elders, and their lawyer won't arrive for another five days (Acts 24:1). The tribune's plan has worked; Paul is safe with the governor, and the tribune doesn't have to deal with the conflict between Paul and the Sanhedrin anymore.