In the Bible, where do unsaved people go when they die?
No Consistent Biblical Treatment of Afterlife
There isn't a full or consistent treatment of this in the biblical texts. The New Testament is more relevant, as it is with the gospel message that people are thereafter categorized as believers or unbelievers. "Unsaved" isn't really a biblical term. The more clear emphasis in the New Testament is that all will face a divine judgement as part of the final events of this world and the ushering in of the new world of God's kingdom. Also, the New Testament texts show more concern to assure that believers who die are not forsaken or lost to God. They are somehow kept in God's purposes and will be resurrected to eternal life in the last judgement. Unbelievers do not share this hope.
Biblical Concepts of Afterlife
It seems like the question should be an easy one, but it’s not since the biblical view on this evolves over time. During most of the Old Testament period, there really wasn’t a concept of an afterlife at all. To the degree that a soul continued to exist after death, it was just a grey, nondescript and emotionless existence known as Sheol and everybody went there, people and animals alike, the wicked and the righteous. The word itself means “the grave pit” in Hebrew and thus was viewed as the common grave for all living.
After the Babylonian exile, the ideas shifted a bit, and you start to get the word Gehenna to denote more of a place of torment. When Judaism came in contact with the Greeks after the conquests of Alexander the Great, Greek thought came with it and beliefs about what happens after death evolved yet again starting in the decade before the birth of Jesus. Some parts of Judaism believed there was no life after death at all, while some believed that the dead were resurrected.
In Jesus day, those two beliefs were represented in the Sadducees (the priestly class who believed there was no life after death) and the Pharisees (who believed in resurrection). Paul skillfully uses that difference to distract from charges brought against him at the beginning of Acts 26 where he gets the Pharisees and Sadducees to fight amongst themselves over the issue of resurrection.
This article from the Encyclopedia Britannica looks at the concepts in a number of religions and if you look over the entries for Judaism and Christianity, you can see how the ideas evolved. That evolution can be seen in the Bible as well. https://www.britannica.com/science/death/Mesopotamia.
There are lots of rabbit holes to run down in all this. The words “heaven” and “hell” in Christian thought today usually mash together lots of concepts that are quite different in the Bible. All that is interesting, but I always encourage people to focus in a different area altogether.
As a Christian, when I get confused by the thousands of years of evolving teaching across the Bible—when the Word made words is giving me trouble, I turn to the Word made flesh in Jesus. To me, that’s part of who Jesus is—the physical example of what the Bible is trying to teach us. Jesus is the multi-media version of the Bible, if you will. Confused about the law? Here, look at this guy. This is what it’s supposed to look like if you’re doing it right.
When I take your question and run it through the filter of the life and teachings of Jesus, two things stand out:
1. In Luke 10:25, a lawyer asks Jesus “What must I do to inherit eternal life?” The answer is so obvious that Jesus makes the guy answer it himself: “You shall love the Lord your God with all your heart, and with all your soul, and with all your strength, and with all your mind; and your neighbor as yourself.” Jesus then confirms that is the right answer and says simply, “Do this, and you will live.”
The lawyer would like a loophole to possibly exclude some people from the “love your neighbor” part and he gets the Parable of the Good Samaritan in response. No loopholes. But the initial question is simply about what it means to be saved and the answer is as easy to grasp as it is hard to live: Love God and your neighbor as yourself.
2. The only time Jesus really describes a final judgment of human souls is in Matthew 25: 31-46. There we get more detail about what loving our neighbors looks like: Feeding the hungry, clothing the naked, welcoming the stranger, visiting those sick and in prison, etc. That’s it. If you do that, you go with the sheep, if not, you’re off with the goats.
3. In both of those places, being “saved” is equated with how we care for others, not some intellectual belief or profession of faith. Our professions are only words unless they result in the fruit of loving God and our neighbors as ourselves.
When dealing with the question of where those sheep and goats are off to, the last line in verse 46 is the most important in my view.
You can do all kinds of word studies on the word for punishment in the first part. Some see “eternal punishment” as everlasting torture in some form, which to me is about as far removed from the judgment of a loving God as you can get. Even if I sinned every day from my first breath to my last, it’s still a finite amount of sin and eternal torment isn’t even a fair judgment for a limited crime, let alone being compatible with a just and merciful God.
But when you combine it with the second part of the sentence, you see that "eternal punishment" and "eternal life" are set up as opposites. In other words, the wicked get death and the righteous get life.
That makes sense to me. I see the Matthew 25 passage as saying: For those who can’t manage to love others, even a little bit, and who have no remorse for that inaction, those souls will, after death, cease to be. They will die eternally in the sense that there will be no resurrection for them, (not that the painful process of dying will torment them forever). On the other hand, those who have shown their love of God by loving their neighbors will live eternally in whatever state God has prepared for them.