The verse highlights God's ability to establish believers firmly in their faith through the gospel of Jesus Christ. This gospel, which Paul refers to as 'my gospel,' is the good news he has been entrusted to share. It centers on the life, death, and resurrection of Jesus, offering salvation to all who believe. The 'mystery' mentioned refers to God's plan of salvation, which was hidden for ages but is now revealed through Christ. This mystery includes the inclusion of the Gentiles into God's covenant, a radical and transformative revelation for the early church.
Paul emphasizes that this revelation was not a last-minute addition but part of God's eternal plan, now made manifest. The verse reassures believers that their faith is grounded in a divine plan that transcends time, offering them stability and strength. It invites Christians to embrace the gospel's power, allowing it to establish them in their spiritual journey, and to trust in God's unfolding plan, which has been revealed through Jesus Christ.