What does Acts 23:17 mean?

Two days prior, Paul went to the temple to fulfill a religious requirement. His intent was to prove his faithfulness as a Jew (Acts 21:20–24). While there, Jews from the province of Asia, making up much of southwest modern-day Turkey, erroneously accused him of letting a Gentile from Ephesus come into the temple. Paul's accusers incited a mob that tried to kill Paul, but the Roman tribune, a military officer, took Paul into custody for his protection (Acts 21:27–36).

A group of forty Jews—possibly these men from Asia—have made a vow to kill Paul before they eat or drink again. To do so, they've enlisted the help of the Sanhedrin who are more than happy to be rid of the man who has been nothing but a thorn in their side ever since he met Jesus. The plan is for the Sanhedrin to ask the tribune to bring Paul to them again, and for the men to assassinate him while he is in transit (Acts 23:12–15).

However, Paul's nephew hears about their conspiracy and goes to the barracks to tell Paul (Acts 23:16). Paul asks a centurion for help. Throughout his ministry, Paul maintains a seemingly good relationship with members of the Roman military. The tribune has already saved his life twice and now will do so again. One of the centurions stopped Paul from being scourged and another will protect him from being killed during a storm (Acts 22:25–26; 27:42–43). When Paul is under house arrest in Rome, he will lead his guards to Christ (Philippians 4:22).

"Young man" suggests Paul's nephew is past puberty but not yet old enough to marry. A tribune is typically a minor nobleman, around 27 years old, who takes a turn in the military for career broadening before moving on into politics. Centurions are officers in charge of about 100 legionnaires.