The issue of “assurance of salvation” seems to me to be one in which most lay Christians are profoundly confused. I think the Bible’s way of talking about things is far clearer and simpler than a lot of people take for granted.
Paul describes the work of the apostles as follows: “So we are ambassadors for Christ, since God is making his appeal through us; we entreat you on behalf of Christ: be reconciled to God. For our sake God made the one who knew no sin to be sin, so that in him we might become the righteousness of God” (2 Cor. 5:20-21).
Salvation is the reconciliation of the human being with God. It is the restoration of friendship between creature and Creator. Being saved means being God’s friend. Because it is a matter of a relationship, there are therefore two sides to the equation.
As far as God’s side is concerned, I think the testimony of the Bible is clear: God accepts us for Jesus’s sake. God sent His only Son into the world to be the atoning sacrifice for our sins (1 John 4:10). It is therefore obvious that God does not desire the death of the wicked (Ezek. 18:32). We do not have any reason to doubt God’s intentions toward us. He wants our friendship more than He wants to uphold His honor or punish sinners or anything of the sort.
As far as our side is concerned, each person has to interrogate him- or herself and determine where his or her heart really lies. The Bible often encourages us to examine ourselves. John writes for example: “Whoever says, ‘I have come to know him,’ but does not obey his commandments is a liar, and in such a person the truth does not exist” (1 John 2:4). This is how we know that our friendship with Jesus is a genuine one: we obey His commandments.
Does John mean that we cannot be sure of anything unless we obey Jesus’s commandments perfectly? No, clearly not. He says just before this: “I am writing these things to you so that you may not sin. But if anyone does sin, we have an advocate with the Father, Jesus Christ the righteous” (1 John 2:1). Clearly John does not envision that we have no hope if we ever sin. To the contrary, God provides His Son for us as an advocate. He gives us an advocate whose intercession He can never turn down.
But it is also true that our obedience to the commandments of Jesus is good measure — not of God’s feelings towards us, but of how serious we are about being His students and disciples. Consider any other sort of friendship. A person can tell how close a friend he or she is with someone else. One can distinguish for example between being friends and being friendly. We must therefore ask ourselves this question with respect to our relationship with God. We can be sure that God loves us and desires our salvation. But how do we feel about Him? Do we wish to live with Him? Do we wish to be the sort of people He has taught us to be through His Son? Or are we actually interested in something else? Are we simply and superficially “friendly” with God? Or can we say honestly that we are friends?
This is what I think the Bible teaches on the matter of “assurance of salvation”. We can be sure of God’s goodness toward us because of Christ’s sacrifice, but we must be wary of our own wandering hearts and be honest with ourselves. God accepts us as His children in Christ. He does not want us to bother about that. He wants us to bother about living in the world as His children. But we must ask ourselves whether we do accept Him as our Father.