How do we know that Christ's atoning work is effective?

The effectiveness of Christ's atoning work lies rooted in the eternal covenant between the Father and the Son. In John 6:39, we read that Jesus will lose none of all those the Father has given Him, providing an assurance that His death was not in vain but accomplished the salvation of all the elect. Christ's work is characterized not as an uncertain attempt but as a definitive act ensuring that all His sheep will be gathered into the fold. His blood secures an unbreakable promise that culminates in the eventual salvation of every believer, thus establishing the doctrine of perseverance and the certitude of grace in sovereign election.