Andy Naselli has some resources by Don Carson on the topic of assurance of salvation. These are highly recommended.
- D. A. Carson and John D. Woodbridge, Letters Along the Way: A Novel of the Christian Life (Wheaton: Crossway, 1993), 15–25 (letters 2 and 3).
- D. A. Carson, “Johannine Perspectives on the Doctrine of Assurance,” Explorations10 (1996): 59–97.
- ———. “Reflections on Christian Assurance,” in Still Sovereign: Contemporary Perspectives on Election, Foreknowledge, and Grace (ed. Thomas R. Schreiner and Bruce A. Ware; Grand Rapids: Baker, 2000), 247–76.
- ———. “The Johannine Letters,” in New Dictionary of Biblical Theology (ed. T. Desmond Alexander and Brian S. Rosner; Downers Grove: IVP, 2000), 351–55.
- ———. “The SBJT Forum: Granted that there are spurious conversions in the Bible, what criteria help us to discern that a profession of faith is genuine?” The Southern Baptist Journal of Theology 5, no. 1 (2001): 78–81.
- ———. Five-part sermon series on 1 John.
Regarding the first resource, it’s a compilation of letters written between a wise, elderly seminary professor and a young, struggling Timothy who is learning what it means to live out his life in Christ. Through fiction, Carson and Woodbridge have architected a manual for discipleship from which every pastor can learn a tremendous amount and in which every believer can find rich and rewarding salve for the troubled soul. The application of grace coupled with sage advice spills from every page.
Throughout these exchanges, the good professor engages young Timothy’s concerns with eloquence and relevance. For me, one of the most penetrating and encouraging passages written by the elder are these words at a time when Timothy’s guilt and despair were at an all-time high. Listen carefully to this solidly biblical and pastorally gracious advice regarding our assurance of salvation:
Since becoming a Christian, you have become more and more aware of the sin in your life, and you are discouraged by it. But what discourages you, I see as a sign of life—not the sin itself, but the fact that you are discouraged by it. If you professed faith in Christ and it did not make any difference to your values, personal ethics, and goals, I would begin to wonder if your profession of faith in Christ was spurious (there are certainly instances of spurious faith in the Bible—for instance, John 2:23-25; 8:31ff.).
But if you have come to trust Christ, then growth in Him is always attended by deepening realization that you are not as good as you once thought you were, that the human heart is frighteningly deceptive and capable of astonishing depths of selfishness and evil. As you discover these things about yourself, the objective ground of your assurance must always remain unfalteringly the same: ‘if anybody does sin we have one who speaks to the Father in our defense—Jesus Christ, the Righteous One’ (1 John 2:1). Let your confidence rest fully in that simple and profound truth.
What you will discover with time is that although you are not as holy as you would like to be or as blameless as you should be, by God’s grace you are not what you were. You look back and regret things you have said and thought and done as a Christian; you are embarrassed perhaps by the things you failed to think and say and do. But you also look back and testify with gratitude that because of the grace of God in your life, you are not what you were. And thus, unobtrusively, the subjective grounds of assurance also lend their quiet support.
(p. 23)