We are not the final arbiters of anyone’s final destiny. To me, that is a supremely important thing to grasp. We have relatively poor measures to understand all that God does in the lives of people who sin, and there are clearly very grievous sins that Christians commit.
Scripture constantly urges us not to receive the grace of God in vain in our lives regarding the way we understand how God’s grace works. God’s grace always reigns through righteousness in our lives. In a sense, it seems to be our chief responsibility not to speculate about, “What may happen if—,” but to respond to our own sin the way Scripture encourages us to respond to it; that is, to resist it with all our might and main.
It is possible to commit grievous sins like Simon Peter. My own conviction is that if you’d bumped into Simon Peter on the evening of Christ’s crucifixion, and then you bumped into Judas Iscariot, you would not have been able to tell the difference. What made the difference was the intercession of Christ for Simon Peter that led to his repentance.
Again and again in Scripture we see this. Hebrews chapter 6 is a notable example. It’s possible to experience many aspects of the power of the kingdom of God and yet, as I understand that passage, not actually experience salvation. He says in Hebrews 6:9, “We are persuaded of better things of you.” There, Hebrews is urging us: “Do not mistake the things that accompany salvation in your life for the reality of repentance towards God and faith in our Lord Jesus Christ.”
I think these two things give us balance. We are not the final judge of anyone’s life. We don’t know what happens in the secret places of people’s minds, even when they sin in their last breath, but we do have a responsibility for ourselves. This is how Jesus responds to that kind of question when He is asked, “Are there going to be many who will be saved or many who will be lost?” He responds, “Make sure you are” (Luke 13:23–24). When we do that, we refocus on the things that are central and we know that the Judge of all the earth does right.