What are Good Works?
Good works are only those which God has commanded in His holy Word. Works which do not have such warrant, and are invented by people out of blind zeal or on pretence of good intentions, are not good works.
These good works, done in obedience to God's commandments, are the fruits and evidence of a true and living faith. By them believers express their thankfulness, strengthen their assurance, edify their brethren, enhance their profession of the Gospel, and silence the opponents [of the Gospel]. So they glorify God whose workmanship they are, created in Christ Jesus to do good works and to produce the fruits of holiness which lead to eternal life.
Their ability to do these good works does not in any way come from themselves, but entirely from the Spirit of Christ. To enable them to do good works (besides the graces they have already received) they require the actual influence of the Holy Spirit to cause them to will and to do His good pleasure. Yet are they not on this account to become negligent, nor to think that they are not required to perform a duty unless given a special impulse of the Spirit; rather, they ought to be diligent in stirring up the grace of God that is in them.
Those who in their obedience [to God] attain the greatest height possible in this life, are still far from being able to perform works of supererogation (that is, to do more than God requires) since they fall short of much which, as their duty, they are required to do.
We cannot, even by our best works, merit pardon of sin or eternal life from the hand of God, for those works are out of all proportion to the glory to come. Moreover, because of the infinite distance that is between us and God, our works can neither benefit God nor satisfy the debt of our former sins. When we have done all we can, we have only done our duty, and are still unprofitable servants. Besides, if our works are good they originate from the Spirit, and whatever we do is defiled and mixed with so much weakness and imperfection that it cannot endure the severity of God's judgment.
Yet, although believers are accepted as individual people through Christ, their good works also are accepted in Christ. It is not as though in this life they were entirely blameless and beyond censure in God's sight, but that He looks upon them in His Son, and is pleased to accept and reward what is sincere, even though it is accompanied by many weaknesses and imperfections.
As for works done by the unregenerate, even though in essence they may be things which God commands, and may be beneficial both to themselves and others, yet they remain sinful works because they do not proceed from a heart purified by faith, nor are they done in a right manner according to the Word, nor is their purpose the glory of God. Therefore such works cannot please God nor make a person acceptable to receive grace from God. Yet the neglect of such works is even more sinful and displeasing to God.