Why is Christ's obedience essential for salvation?

The obedience of Christ is essential for salvation as it fulfills the requirements of God's law, which humanity cannot meet due to sin. Romans 5:18 states, 'Therefore as by the offense of one judgment came upon all men to condemnation; even so by the righteousness of one the free gift came upon all men unto justification of life.' This illustrates that through Christ's obedience, believers receive the free gift of justification, meaning their sins are forgiven, and they are declared righteous in God's sight solely because of Christ's merit, not their own.