Although temporary believers and other unregenerate men may vainly deceive themselves with false hopes and carnal presumptions that they are in the favor of God and in a state of salvation, such a hope on their part will perish. Yet those who truly believe in the Lord Jesus and love him in sincerity and who endeavor to walk in all good conscience before him may be certainly assured in this life that they are in the state of grace and may rejoice in the hope of the glory of God. And such a hope shall never make them ashamed.
This assurance is not merely a conjectural persuasion nor even a probable persuasion based upon a fallible hope. It is an infallible assurance of faith founded on the blood and righteousness of Christ revealed in the gospel. It is also founded upon the inward evidence of those graces of the Spirit in connection with definite promises made in the Scriptures, and also on the testimony of the Spirit of adoption who witnesses with our spirits that we are the children of God, and who uses the experience of assurance to keep our hearts both humble and holy.
This infallible assurance is not so joined to the essence of faith that it is an automatic and inevitable experience. A true believer may wait long and fight with many difficulties before he becomes a partaker of it. Yet, being enabled by the Spirit to know the things which are freely given to him by God, he may, without any extraordinary revelation attain this assurance by using the means of grace in the right way. Therefore it is the duty of everyone to give the utmost diligence to make his calling and election sure, so that his heart may be enlarged in peace and joy in the Holy Spirit, in love and thankfulness to God, and in strength and cheerfulness for carrying out the duties of obedience. These duties are the natural fruits of assurance, for it is far from inclining men to looseness [i.e., to be unrestrained in their behavior].
True believers may have the assurance of their salvation in various ways shaken, diminished, or intermitted. This may be because of their negligence in preserving it, or by their falling into some special [= specific] sin which wounds the conscience and grieves the Spirit, or by some sudden or forceful temptation, or by God’s withdrawing the light of his countenance, and permitting even those who fear him to walk in darkness and to have no light. Yet, believers are never left without the seed of God and life of faith, that love of Christ and the brethren, that sincerity of heart, and that conscience about their spiritual duty. Out of these things, by the operation of the Spirit, their assurance can in due time be revived, and in the meantime the presence of these graces preserves them from utter despair.