True evangelical religion is here represented as a building, the foundation of which is laid in the faith of Christ: “Building up yourselves on your most holy faith.” Whether it relate to personal or to social religion, this must be the foundation of the fabric, or the whole will fall. Many persons are awakened to some serious concern about futurity, and excited to inquire what they must do to be saved; and, in that state of mind, it is not unusual for them to have recourse to reading and prayer, as a preparation for death. Many preachers, too, will think it sufficient to direct them to the use of these means. But if the death and mediation of Christ be overlooked, it is not reading, or prayer, or any other religious exercise, that will avail us. Why did John the Baptist, Christ, and his apostles lay the foundation of the gospel kingdom by calling on sinners to “repent and believe the gospel?” Was it not because all other duties, prior to these, were of no account? When some, who followed Christ for loaves, inquired what they must do to work the works of God, his answer was, “This is the work of God, that ye believe on him whom he hath sent;” plainly intimating that no work, prior to this, could be pleasing to God. The Scriptures direct men to pray, but it is in faith. To the question, “What must I do to be saved?” there is but one answer—“Believe on the Lord Jesus Christ, and thou shalt be saved.” Christ is the door; by him if any man enter in he shall be saved. To direct inquirers to any thing short of this is to direct them to that which, if complied with, will leave them short of salvation. This the Scriptures never do: there is not a direction in the oracles of God but, if truly followed, will lead to everlasting life.
One lays the foundation of his religion in what he calls reason; but which in fact is his own reasoning. The same inspired writer who in one sentence commends understanding, in the next warns us against leaning to our own understanding. To strengthen ourselves and one another in this way, is to build up ourselves on our own conceits. Another founds his religion on his good deeds. Good deeds undoubtedly form a part of the building, but the foundation is not the place for them. They are not the cause, but the effects of faith. They prepare us for heaven, as meetening us for it, but not as rendering us deserving of it. A third builds his religion on impressions. It is not from the death of Christ for sinners or any other gospel truth that he derives his comfort, but from an impulse on his mind that his sins are forgiven, and that he is a favourite of God, which is certainly no where revealed in the Scriptures. We may build ourselves up in this way, but the building will fall. A fourth founds his religion on faith, but it is not a holy faith, either in respect of its nature or its effects. It is dead, being alone, or without fruit. The faith on which the first Christians built up themselves included repentance for sin. As when forgiveness is promised to repentance, faith in Christ is supposed; so when justification is promised to believing, repentance is supposed. However distinct they are, as to their nature and objects, they have no separate existence. Hence, in the preaching of John, Christ, and the apostles, they are united; and hence the faith of Christ; supposing a renunciation of every thing opposed to it, and including a cordial acquiescence in the gospel way of salvation through his death, is most holy.
Fuller, A. G. (1988). “Principles and Prospects of a Servant of Christ (Jude 21, 22), Sermon XXVII. The Complete Works of Andrew Fuller: Memoirs, Sermons, Etc. (J. Belcher, Ed.; Vol. 1, pp. 342–343). Sprinkle Publications.