How do we know Christ's work for salvation is complete?

The assurance of Christ's completed work is found in His declaration, 'It is finished,' at Calvary, which signifies that all the requirements of the law and justice of God have been satisfied. The resurrection of Christ further confirms this, as it showcases His victory over sin and death, proving that He successfully accomplished redemption for His people. In 1 Corinthians 15 and Romans 4:25, we see that Jesus was raised for our justification, solidifying the truth that through His death and resurrection, we are fully and completely saved.