What is Assurance of Grace and Salvation?
Temporary believers and other unregenerate people may deceive themselves with futile and false hopes and unspiritual presumptions that they are in favour with God and in a state of salvation, but their hope will perish. Yet those who truly believe in the Lord Jesus, and love Him in sincerity, and endeavour to walk in all good conscience before Him, may be certainly assured in this life that they are in the state of grace; they may rejoice in the hope of the glory of God, knowing that such hope will never make them ashamed.
This certainty is not mere conjecture or probability based on a fallible hope. Rather it is an infallible assurance of faith based on the blood and righteousness of Christ revealed in the Gospel, on the inward evidence of those graces of the Spirit (about which promises have been made), and on the testimony of the Spirit of adoption who witnesses with our spirits that we are the children of God. As the fruit of this assurance, the Spirit keeps our hearts both humble and holy.
This infallible assurance is not an essential part of faith, for a true believer may wait a long time, and struggle with many difficulties before obtaining it. Yet we may obtain it without extraordinary revelation and by the right use of ordinary means, for we are enabled by the Spirit to know the things which are freely given to us by God. Therefore it is the duty of everyone to be as diligent as possible to make their calling and election sure, so that their hearts may be enlarged in peace and joy in the Holy Spirit, in love and thankfulness to God, and in strength and cheerfulness in carrying out the duties of obedience. These duties are the natural fruits of this assurance, for it is far from inclining people to lose living.
In various ways true believers may have their assurance of salvation shaken, diminished, or interrupted. This may be because of their negligence in preserving it, or by falling into some particular sin which wounds the conscience and grieves the Spirit, or by some sudden or forceful temptation, or by God withdrawing the light of His countenance and causing even those who fear Him to walk in darkness and to have no light. Yet believers are never destitute of the seed of God and the life of faith, the love of Christ and the brethren, sincerity of heart and conscience of duty. Out of these things, this assurance may in due time be revived by the operation of the Spirit, and in the mean time they are preserved from utter despair.