How do we know that believers are eternally secure in Christ?

Eternal security is a cornerstone of sovereign grace theology, underscored by the belief that once a person is truly saved, they cannot lose their salvation. Jesus declares in John 10:28-29 that His sheep shall never perish, and no one can snatch them out of His hand. This security is rooted in the sovereign will of God, who has decreed the salvation of His elect before the foundation of the world (Ephesians 1:4-5). The grace that saves is also the grace that sustains; thus, when a person is genuinely converted, the holy fire of grace, once kindled in their heart, does not extinguish, ensuring that they will persevere in faith until glorification.