How do we know justification by Christ alone is true?

The concept of justification being through Christ alone is reinforced throughout the New Testament, particularly in Romans and Hebrews. Christ's sacrifice is not only sufficient but complete. When He declared, 'It is finished,' He affirmed that all that is required for justification before God was achieved by Him alone. This is echoed in Hebrews 10:10, which states, 'By that will we have been sanctified through the offering of the body of Jesus Christ once for all.' Thus, our justification rests not on our works but solely on the redemptive work of Christ.