How do we know that Christians will ultimately win the battle over sin?

The assurance of victory for Christians lies in the person and work of Jesus Christ. In 1 Samuel 30:8, God instructs David that he shall surely overtake his enemies and recover all, which foreshadows the ultimate victory in Christ. Christ, depicted as the ultimate David, has already won the victory on our behalf through His death and resurrection. Revelation 17:14 states that the Lamb will overcome because He is Lord of lords and King of kings, and those with Him are called and chosen and faithful. Thus, believers can face their daily battles against sin with confidence, knowing that Christ's sovereign rule guarantees their ultimate victory.