"The dispute became so violent that the commander was afraid Paul would be torn to pieces by them. He ordered the troops to go down and take him away from them by force and bring him into the barracks." NIV translation
The argument over resurrection and spirits got so bad that the commander was afraid for Paul. He had Paul taken into protective custody and kept in the barracks with the soldiers.
"The following night the Lord stood near Paul and said, 'Take courage! As you have testified about me in Jerusalem, so you must also testify in Rome." NIV translation
Before he came to Jerusalem, Paul knew that he was going to be arrested for sharing the gospel. He boldly went ahead because he knew that was God's will for him. Now, the Lord tells him that he must do the same thing in Rome. We may try to elevate Paul as some sort of super Christian as God was using him in a mighty way but God has prepared things for all of us to do (see Ephesians 2:10).It is the same for all of us in that we are all called to testify about Jesus Christ wherever the Lord sends us and in whatever circumstances we find ourselves in.
"The next morning the Jews formed a conspiracy and bound themselves with an oath not to eat or drink until they had killed Paul. More than forty men were involved in this plot." NIV translation
A group of forty Jews made a pact to kill Paul. They pledged that they would not eat or drink until he was dead. These days it seems like people take oaths and give their word with no intention of keeping it but it was not like that during these times. The men were serious and intended to kill Paul before the end of the day.
"They went to the chief priests and elders and said, 'We have taken a solemn oath not to eat anything until we have killed Paul. Now then, you and the Sanhedrin petition the commander to bring him before you on the pretext of wanting more accurate information about his case. We are ready to kill him before he gets here.'" NIV translation
The forty men needed the help of the religious leaders to carry out their plan. They asked them to have another trial and while Paul was on his way to appear they would ambush him. This is the same way that Satan usually attacks Christians in that it is rarely a direct frontal assault.