The Heidelberg Catechism says that the Christian’s good works help in the assurance of faith: “we do good so that we may be assured of our faith by its fruits” (Q/A 86). The Westminster Larger Catechism notes under assurance that the Holy Spirit enables Christians to “discern in themselves those graces to which the promises of life are made” (Q/A 80). Biblically speaking, James said that true faith is shown to be true by works (James 2:18) and John wrote that we can tell we have new life when we love other Christians (1 John 3:14).
I appreciate Louis Berkhof’s explanation of how assurance of faith is related to good works in the Christian’s life:
…Reformed Confessional Standards also clearly indicate that assurance is based in part on the so-called syllogism of faith, in which the believer consciously and deliberately compares the graces that adorn his life and his general conduct, with the biblical description of the virtues and the godly conversation of those who are born of the Spirit, and on their relative correspondence bases the conclusion that he is indeed a child of God.
Berkhof ended the section this way – by emphasizing sovereign grace:
…Some object to this method of seeking assurance altogether. They claim that it directs believers to seek the ground of assurance within themselves, and thus encourages them to build on a self-righteous foundation. But this is clearly a mistake. Believers are not taught to regard their good works as the meritorious cause of their salvation, but only as the divinely wrought evidences of a faith that is itself a gift of God. Their conclusion is based exactly on the assumption that the qualities and works which they discover in their life, could never have been wrought by themselves, but can only be regarded as the products of sovereign grace.
(As a side, The Assurance of Faith is only $5.99 on Logos. It’s very much worth that!)
Hammond, WI, 54015