21:37-38 The commander had assumed that Paul was a certain Egyptian who had appeared in Jerusalem three years earlier. This man claimed to be a prophet of God and announced that the wall of Jerusalem would collapse at his command. He further claimed that he would lead his followers from the Mount of Olives into Jerusalem where they would defeat the Romans and throw off their yoke. The Romans, however, attacked this man's followers first and killed many of them, but he had escaped.
The Egyptian's followers came from the ranks of the Assassins (lit. dagger-men). These were radicals who mingled with crowds with daggers hidden under their cloaks and stabbed Romans and pro-Roman Jews stealthily in an attempt to gain Jewish independence from Rome.858
Claudius Lysias evidently thought this man had returned to the temple area to recruit more followers and the people who now recognized him as an impostor had turned against him.
21:39 Paul explained that he was a Jew and so had a right to be in the temple court of Israel. He was not a resident of Egypt but of the respected Roman city of Tarsus. Tarsus was one of the three chief centers of learning in the ancient world, along with Athens and Alexandria. It was also the capital of Cilicia and a free city in the empire.
21:40 These credentials persuaded the Roman commander to let Paul address the mob. Paul motioned with his hand to the crowd, a gesture designed to quiet them and rivet their attention (cf. 12:17). Paul spoke to the Jews in Aramaic, the vernacular of Palestinian Jews, rather than in Greek. This would have helped his hearers realize that he was one of them.