What did Paul mean when he wrote 'to die is gain' (Philippians 1:21)?

from the old testament

• Although Paul is not mentioned in the Old Testament, King David faced significant suffering and persecution. He spent many years as a fugitive, pursued by King Saul (1 Samuel 18—31). David’s life points to Jesus, and that was Paul’s goal also.

from the new testament

• Paul had been faithful to obey God and he had literally presented his body as a living sacrifice (Romans 12:1) for the sake of Christ multiple times.
• Paul's physical death would be a gain for him because it would mean his earthly days were finally finished and he could be with Jesus forever in eternity (Philippians 1:23).
• Even in the midst of his desire to be with Christ, Paul acknowledged that there was still good he could do here on the earth for the Philippian church (Philippians 1:22–26).
• Paul’s imprisonment for the sake of Christ gave other believers greater boldness to share the gospel (Philippians 1:12–14).
• Paul details his suffering in 2 Corinthians 11:16–33: beaten with rods; shipwrecked three times; imprisoned multiple times; surrounded by dangerous situations, such as betrayal, cold, and hunger, etc. He knew that whether in life or in death, he would bring glory and honor to God.

implications for today

When Paul wrote the book of Philippians he was in prison. He expressed how much he prayed and yearned for the people of Philippi and said how much he desired for them to increase in love, discernment, and the fruit of the Spirit (Philippians 1:1–11). He then assured them that "what has happened to me has really served to advance the gospel" (Philippians 1:12) because all of the prison guards came to know his testimony. Though he had desires of where he wanted to be and what he wanted to do, Paul’s ultimate concern was that the gospel was being shared (Philippians 1:15–18).

By the time Paul wrote this, he had already experienced great persecution and suffering for the sake of Christ. This is why, when he gets to Philippians 1:20–21, he says, "it is my eager expectation and hope that I will not be at all ashamed, but that with full courage now as always Christ will be honored in my body, whether by life or by death. For to me to live is Christ, and to die is gain." Most Christians will not be persecuted in ways as extreme as Paul was, yet we still experience the desire to be with our Savior in heaven (2 Corinthians 5:8). This desire, however, should never be an excuse for us to mentally check-out while here on earth and sit around waiting for heaven. We should be actively bringing honor and glory to God with our lives and staying engaged in advancing the kingdom of God here on the earth (Matthew 28:18–20; 2 Peter 3:8–13). Just as Paul sought to honor God in all aspects of his life and stay engaged in his present work, so should we. Then, for all of us, to live will be Christ and to die will be gain.