What does the Bible say about perseverance in salvation?

According to Philippians 1:6, Paul expresses his confidence that He who began a good work in believers will complete it until the day of Christ. This passage emphasizes God's sovereign initiative in salvation, assuring that it is He who sustains and brings His people to glory. The power behind salvation is not the believer’s effort but God's grace. This assurance stems from the Gospel's promise that all for whom Christ died will be saved and sustained by Him throughout their lives, despite their struggles and shortcomings.