Many people assume that by trying to live a good life, they have done all that is necessary to get to heaven. They rest their confidence on the good works they have performed to satisfy the demands of God's justice.
This is a futile hope. God's law requires perfection. Since we are not perfect, we lack the necessary goodness to enter heaven. Thus goodness can never be achieved by living a good life. We can only receive it by trusting in the righteousness of Christ. His merit is perfect and is made available to us through faith.
To believe that we are justified by our good works apart from faith is to embrace the heresy of legalism. To believe that we are justified by a kind of faith that produces no works is to embrace the heresy of antinomianism.
The relationship of faith and good works is one that may be distinguished but never separated. Though our good works add no merit to our faith before God, and though the sole condition of our justification is our faith in Christ, if good works do not follow from our profession of faith, it is a clear indication that we do not process justifying faith...When James declared that faith without works if dead, he asserted that such "faith" cannot justify anyone because it is not alive. Living faith produces good works, but these good works are not the basis for justification. Only the merit achieved by Jesus Christ can justify the sinner.
It is a grievous error, indeed a modern form of the antinomian heresy, to suggest that a person can be justified by embracing Jesus as Savior but not as Lord. True faith accepts Christ as both Savior and Lord. To rely on Christ alone for salvation is to acknowledge one's total dependence upon Him and repent of one's sin. To repent of sin is to submit to Christ's authority over us. To deny His lordship is to seek justification with an impenitent faith, which is not faith.
Adapted from the Reformation Study Bible.