Pauls presence on the Temple Mount in 57 AD started a riot because the some Jews visiting from Ephesus who have had to tolerate Paul in their city stir up a riot among the local Jerusalem Jews by claiming that Paul brought a Gentile, Trophimus of Ephesus, through the court of the Gentiles into the inner courts of the temple. These inner courts were reserved for Jews and were clearly marked by several stone inscriptions. Josephus, an eyewitness of the pre-70 AD Temple describes this barrier this way:
Anyone passing through this towards the second court found it enclosed within a stone balustrade four and a half feet high, a perfect specimen of craftsmanship. I this at equal intervals stood slabs announcing the law of purification, some in Greek and some in Roman characters. No foreigner was to enter the holy area this was the name given to the second court. (details)
Archaeology has discovered two of these slabs that announced, no foreigner was to enter the holy area. The stones are written in Greek and say:
No foreigner is to enter within the forecourt and the balustrade around the sanctuary. Whoever is caught will have himself to blame for his subsequent death. (See image and details here and here)
The crowd mobbed around Paul, who was a man from a Gentile city of Tarsus and was known to teach and travel with Gentiles. But, when Paul raised his voice and began to speak to them in Aramaic instead of his native Greek, Luke says the crowd became very quiet. (Aramaic is, like Hebrew, a Semitic language and very similar to Hebrew. It was the native language of Judea in Jesus and NT times.) If Paul had spoken Greek to this Jewish crowd on the Temple Mount the riot would have, most likely, continued. Instead, the Jewish crowd becomes quiet and listens to this Gentile-looking, Gentile-loving Jew from Gentile-Cilicia. They even listen to him talk about a vision from heaven and the Lord appearing to him, that is, until he said that God told him, Go; I will send you far away to the Gentiles.
Those words revealed Pauls attitude that had caused this crowd of Jews to riot in the first place. When they heard Paul admit this, they raised their voices and shouted, Rid the earth of him! Hes not fit to live! Paul would spend the next five years (57-62 AD) tied up in a legal battle with the Jews that would take him all the way to Rome to appear before Emperor Nero before he would be set free.