The Heidelberg Catechism
Questions and Answers 62-64, 86, 91
Q. 62. But why cannot our good works be the whole, or part of our righteousness before God?
A. Because, that the righteousness, which can be approved of before the tribunal of God, must be absolutely perfect, and in all respects conformable to the divine law; and also, that our best works in this life are all imperfect and defiled with sin.
Q. 63. What! do not our good works merit, which yet God will reward in this and in a future life?
A. This reward is not of merit, but of grace.
Q. 64. But doth not this doctrine make men careless and profane?
A. By no means: for it is impossible that those, who are implanted into Christ by a true faith, should not bring forth fruits of thankfulness.
Q. 86. Since then we are delivered from our misery, merely of grace, through Christ, without any merit of ours, why must we still do good works?
A. Because Christ, having redeemed and delivered us by His blood, also renews us by His Holy Spirit, after His own image; that so we may testify, by the whole of our conduct, our gratitude to God for His blessings, and that He may be praised by us; also, that everyone may be assured in himself of his faith, by the fruits thereof; and that, by our godly conversation, others may be gained to Christ.
Q. 91. But what are good works?
A. Only those which proceed from a true faith, are performed according to the law of God, and to His glory; and not such as are founded on our imaginations, or the institutions of men.