How do we know that God's grace ensures our salvation?

The assurance of salvation through grace is rooted in the understanding that it is a gift from God, as encapsulated in Ephesians 2:8-9, which states that we are saved by grace through faith, and that not of ourselves; it is the gift of God, not of works lest anyone should boast. This underscores the belief in sovereign grace, particularly that our salvation is solely reliant on God’s unmerited favor and His choice to call us. God's grace ensures that once He has chosen to call and save an individual, that salvation is secure, and cannot be lost.