Why is the phrase 'It is finished' so important in Christianity?

The phrase 'It is finished' (Teleho in Greek) encapsulates the entirety of Christ’s redemptive work. At that moment, Jesus affirmed that all prophecies regarding the Messiah were fulfilled, every requirement of the law was satisfied, and the atonement for sin was completed. This is highlighted in John 17:4, where Jesus states, 'I have finished the work which Thou gavest Me to do,' reinforcing that His mission was successfully accomplished. For Christians, these words bring immense peace and assurance, confirming that salvation is secured and rests solely on the finished work of Christ, freeing believers from the burden of striving for righteousness through their own efforts.