In Acts 21, we read about Paul being arrested in Jerusalem at the Temple. Here is Bob Deffinbaugh’s commentary, from Bible.org, on this passage:
Paul’s Skillful Use of Language
37 As Paul was about to be brought into the barracks, he said to the commanding officer, “May I say something to you?” The officer replied, “Do you know Greek? 38 Then you’re not that Egyptian who started a rebellion and led the four thousand men of the ‘Assassins’ into the wilderness some time ago?” 39 Paul answered, “I am a Jew from Tarsus in Cilicia, a citizen of an important city. Please allow me to speak to the people.” 40 When the commanding officer had given him permission, Paul stood on the steps and gestured to the people with his hand. When they had become silent, he addressed them in Aramaic, 1 “Brothers and fathers, listen to my defense that I now make to you.” 2 (When they heard that he was addressing them in Aramaic, they became even quieter.) (Acts 21:37—22:2a, emphasis mine)
The Roman commander had no idea who Paul was when he extracted him from the hands of those at the temple who sought to tear him to pieces. He bound Paul with chains and asked him who he was and what he had done. All this took place while the crowd was screaming for Paul’s blood and making contradictory accusations. He could not even hear because the roar of the crowd was so great, so he brought Paul into the barracks to question him. When they were almost to the barracks, Paul asked to speak to the commander, in Greek. The commander was taken aback because of the possibility (likelihood?) that Paul was the Egyptian revolutionary who had started a rebellion and led 4,000 assassins into the wilderness. It would seem that Paul’s skillful use of the Greek language caught the commander completely off guard (pardon the pun), and set his mind at ease that Paul was not a revolutionary.
Paul assured the commander that he was not the Egyptian revolutionary; he was a Jew from the city of Tarsus in Cilicia, a most important city. Paul took advantage of the moment and asked the commander if he could speak to the crowd. Perhaps this seemed like a good idea to the commander because he would be able to hear what Paul had to say, and in doing so, perhaps he could make a determination as to what the charges against him, if any, should be.
Was this poor fellow ever in for a surprise. When the commander granted him permission, Paul signaled to the crowd that he wanted to speak. When a hush fell over the crowd (a lot of them wanted to know what this was all about) Paul began to speak – in Aramaic. That silenced the crowd even more, but it surely caught Claudius Lysias by surprise. How could he possibly understand Paul and thus be able to discern what the issues were? This was also true of the Hellenistic Jews. Many (perhaps most) of them would not have been fluent in Aramaic, and so they would have to listen very carefully if they were to understand anything he said. Paul now had everyone’s attention.