I write these things to you who believe in the name of the Son of God, that you may know that you have eternal life. (1John 5:13)

It is not uncommon for a genuine believer (one who personally believes in the person and work of Jesus Christ as being the only way of eternal life and to have sins forgiven) to have times of doubt concerning the reality or the certainty of their salvation. 

When as a younger believer I often doubted my security in Christ. This resulted in a lack of personal assurance that I was truly forgiven by God. This lead to a personal fear that I was not saved at all and that eternal hell was ever before me. 

The problem was, I was resting on how I felt. I was basing my assurance, or lack of it on the subjective notions produced by the mind, especially when I chose to sin, or I was not living like I thought ‘good Christians’ should. During these times (and we all have them) despair, turmoil and doubt invade and rob us of the trust we had in God’s truth.

And might I say - this is exactly what happens. We loose sight of God’s objective truth concerning the gospel and what God has done and promised and give way to the overpowering subjective doubts and notions of our fickle minds. 

Don’t’ get me wrong! There is a subjective element in our assurance. The Holy Spirit gives witness in our hearts/minds that we belong to God. But that only comes as we submit our hearts and minds to the objective truth of God’s word. (Rom. 6:11) 

1John is full of ‘tests” that we can run by our lives to measure the reality of our salvation. That is what our text is speaking of when it says, “I write these things that you may know that you have eternal life.” 

I like how simply Jerry Bridges puts this:
Three means by which God assures us that we do have eternal life:
1. The promises of His Word
2. The witness of the Spirit in our hearts
3. The transforming work of the Spirit in our lives.