What does Acts 20:31 mean?

The warning from Paul is serious. He has told elders of Ephesus that false teachers will infiltrate their church and try to drag people away from following Jesus (Acts 20:28–30). The elders are now responsible for doing everything they can to keep this from happening. To protect their congregation, they will need to follow Paul's example: to be always ready and to passionately tell the people what they need to hear.

Later, Paul will remind the elders how he lived modestly and met his own expenses so that those he ministered to would not be distracted by an obligation to support him and his team (Acts 20:33–35). Pastors and elders need to be willing to make significant sacrifices for those they serve.

It's unclear how Paul was in Ephesus for three years. He spoke in the synagogue for three months and then built the church in the hall of Tyrannus for two years (Acts 19:8–10). Luke doesn't say if there was a break between the synagogue and the hall or if one of the numbers is rounded. Either way, it's the longest Paul spends in any of the churches he plants—the runner-up being Corinth where he stays initially for a year and a half and then again for three months (Acts 18:11; 20:3).

Unlike Paul's other churches, he does not return to Ephesus or see the elders again after this meeting (Acts 20:25). He leaves them with a warning of future spiritual warfare in a city filled with witchcraft, but he commends them to God and His grace to build them up (Acts 20:32).