“And as they went about to kil him, tidings came vnto the chiefe captaine of the band, that all Hierusalem was in an vprore.”
1611 King James Version (KJV)
21:31 And as they went about to kill him - It was a rule among the Jews, that any uncircumcised person who came into the inner temple, might be stoned without farther process. And they seemed to think Paul, who brought such in thither, deserved no better treatment. Word came to the tribune - A cohort or detachment of soldiers, belonging to the Roman legion, which lodged in the adjacent castle of Antonia, were stationed on feast days near the temple, to prevent disorders. It is evident, Lysias himself was not present, when the tumult began. Probably he was the oldest Roman tribune (or colonel) then at Jerusalem. And as such he was the commanding officer of the legion quartered at the castle.
Ac 21:31 They went about to kill him. Had Trophimus been within, their customs might have permitted them to kill him, but to slay Paul could only be a murder. Tidings came unto the chief captain. The commander of the garrison in the castle of Antonia, overlooking the temple. The watch could see the uproar from their elevated outlook, and the soldiers in a moment would rush down the staircase that led into the temple area, and appear upon the scene. The fortress joined the temple wall and had two flights of stairs leading into the temple courts.