What does Romans 16:4 mean?

The previous verse began with Paul's instruction to his readers to greet Prisca/Priscilla and Aquila, a Christian couple he had worked with both in making tents and in ministry. Their relationship to Paul is detailed in other passages of Scripture (Acts 18:18–19; 1 Corinthians 16:19). They are also credited with educating a passionate-but-uninformed man, Apollos, giving him a better understanding of the gospel (Acts 18:26).

In addition to Paul's long and close relationship with these two, he describes them as having "risked their necks." The Greek phrase here serves the same symbolic role as the English translation: these two risked their lives to save Paul. We don't have a record of when this happened, but they were likely present when Paul was nearly killed during a riot in Ephesus (Acts 19:23–41). It may also be a more general reference to their willingness to endure danger and threat of loss for the sake of Paul's mission.

Paul writes that he gives them thanks, likely not just for risking their lives for his sake but also for years of service and close friendship. In addition, he says, all the Gentile churches give thanks for this couple, as well. Perhaps Paul means that all these churches are grateful that Paul lived to finish his ministry because of Priscilla and Aquila or perhaps he is referring to their long service to many different people.