Why is assurance something that even believers seem to struggle with? Because, ultimately, even for believers, it can be hard to believe the gospel.
A Shadow of a Doubt
I grew up in a Christian home, but to be completely transparent, I don’t know the date of my conversion. As I grew into my teenage years and even into adulthood, this presented a very big problem for me. I would hear well-meaning pastors and evangelists speak of salvation experiences that included a time and a place of conversion, but a time and place was not something that I knew. How could I be sure of salvation, “without a shadow of a doubt”?
In the case of myself and many others, this is a real problem that presents a great deal of anxiety. So how can we be assured of salvation?
The Source of an Undecieving Assurance
Chapter 18 of the 1689 London Baptist Confession states that: “infallible assurance of faith founded on the blood and righteousness of Christ revealed in the Gospel.”
The term ‘infallible’ that the framers of the confession use here come from two Latin words which mean, literally, ‘not deceiving’, in essence, not able to be mistaken or deceive.
Sam Waldron explains “This should reassure the one who says, ‘I want to have assurance, but I am so fearful of being mistaken and deceiving myself.’ There is an assurance of salvation which you may have, which will not deceive you”. 
So where do we find the source of this assurance that will not deceive us? The short answer is in the gospel!
I know that I am saved, know God, and am known by God, not because I have seen the Lamb’s Book of Life, or because I know that my faith was sincere, or even because I believe that I repented, but because I know that I am saved because I trust in Christ alone for my salvation. Hard stop!
Looking back over my own experiences, one of the roots of my doubt was a misunderstanding of faith. When we see faith as an action we make or an event that happens, when doubt creeps up we are forced to pull out whatever checklist we may have at the time and begin evaluating our faith. But the scriptures are clear, the faith never belonged to us, to begin with.
Charles Spurgeon explains faith like this, “Faith occupies the position of a channel or conduit pipe. Grace is the fountain and the stream”. 
Faith is the way that the grace of the gospel flowing from Christ’s work gets to us, and the Christian life is described as continually ‘standing in grace’. So how do we get faith? The apostle clearly states that faith comes from hearing the gospel. (Rom 10:17)
If we understand faith correctly (as the channel through which grace flows) then we will find that the “larger” our faith is, then the greater our assurance can be. As stated by Louis Berkhof, “The more our faith grows, the greater will be our assurance”.
Many times our assurance and the display of grace in our lives is due to our “channel” of faith becoming clogged by sin and living in a fallen world. It can even get to the point that the flow of grace becomes so weak that we forget that we ever experienced it. (2 Pet. 1:9)
So how do we increase our faith?
- Don’t trust yourself or your work for assurance. Understand that it is not what you do, or don’t do, that brought salvation to you. But remember that your salvation is found only through the work of Christ for you.
- Connect yourself to a church and enjoy the means of grace. Some have their assurance “shaken, diminished, and intermitted” because they neglect the means of grace by which we come to know our assurance. Connect yourself to an assembly of believers where you are constantly pointed to Jesus. We need to hear the gospel again and again because we are so apt to forget it. At times we need our faith pried open so that grace may flow again.
As believers, we can be most assured of our salvation when we are confident God has forgiven our sins through Christ’s death and resurrection. And we are most confident that God has forgiven our sins through Christ when we hear and remind ourselves of it.
In times of doubt, stop looking into and at yourself for assurance and look outward to the cross, look to the empty tomb, and look to the heavens where He ever liveth for you.
 Reeves, Stan. The 1689 Baptist Confession of Faith in Modern English. (Cape Coral: Founders Press, 2021) 18.4
 Sam E. Waldron. A Modern Exposition Of The 1689 Baptist Confession Of Faith. (Darlington: Evangelical Press, 2013). pp. 279-280.
 Spurgeon, Charles, All of Grace (Chicago: Moody Publishers, 2010), 62-63.
 Berkhof, Louis. The Assurance of Faith (Port St. Lucie: Solid Ground Christian Books, 2004), 62