What does Luke 21:13 mean?

Jesus has warned the disciples that the temple in Jerusalem is going to be destroyed. They want to know the signs that will occur before this happens (Luke 21:5–7). Instead, Jesus gives them a broader overview of what must happen before He returns.

After His ascension and before the temple falls to the Romans, Jesus' followers will face all kinds of persecution; Jesus warned them of this before (Luke 6:22). But this is also a great opportunity. There's little chance a fisherman or a tent maker would get the undivided attention of a governor or a king. Persecution will make this happen (Luke 21:12). At some point, presumably, Paul even speaks to the emperor (Acts 25:11).

Sometimes, this persecution will result in the disciple's death (Acts 12:1–2). At other times, a king will listen intently but ultimately reject the message (Acts 26:28). But sometimes the gospel will succeed, and leaders will turn from their false gods to follow Jesus (Acts 13:12).

This will only be possible because the Holy Spirit, Himself, will give them the words. In fact, they should not try to prepare an argument in advance (Luke 21:14–15). That doesn't mean they shouldn't know how to share about Jesus (1 Peter 3:15). Nor does it mean believers shouldn't think of how to respond to questions or challenges about their faith. Rather, the point is that rather than trying to prepare a "script," or obsess over such things, Christians should let the Holy Spirit guide their words in those moments.