The first gospel written was Mark; we know this because Matthew and Luke quote it, and John regularly counterpoints Luke. And the first thing Jesus says in Mark is this:
Later on, after John was arrested, Jesus went into Galilee, where He preached God’s Good News.
“The time promised by God has come at last!” He announced.“The Kingdom of God is near! Repent of your sins and believe the Good News!” —Mark 1.14-15 NLT
This is a very important scripture because in it, Jesus defines what the gospel is. Which is kinda necessary. For a lot of Christians, what the gospel is, is not as cut-and-dried as you might think.
The word gospel (which the NLT renders “Good News”) translates the Greek word evanghélion, which means good news. (“Gospel” comes from the Old English gōd spel, or “good story,” so naturally it also means good news.)
In the ancient Roman culture, before the Romans invaded a nation, they’d send a messenger (an anghélos) with “good news” (an ev-anghélion). The gospel was, “Our army is coming near! Get ready for it!” And sometimes there’d be a longer story that went along with it: The messenger would talk about the conquering general who led the Roman army, and how awesome he was, what great exploits he had accomplished, what foes he had conquered, and how taking over their nation was gonna be a good thing, ’cause now there was going to be order and stability and peace and democracy. Unless you were anti-Roman, in which case there were going to be a lot of crucifixions.
Anyway, that’s the word that Jesus used, and that’s the word His followers used. Jesus’s gospel was that the Kingdom of God was approaching, and the longer story—the four books in the New Testament that we call the Gospels—is about the conquering King, how awesome He is, what He did and taught and how He conquered death, and how taking over the world was going to be a good thing. Unless you’re anti-God, in which case there’s hell.
Now, when the Romans proclaimed their gospels, of course not everyone believed them. They figured the Romans would be stopped by their armies, or that Roman rule wouldn’t be as great as the Romans were making it out to be. Same deal with Jesus: Not everyone believes the Kingdom of God is actually coming. Not everyone feels they need to repent of their sins, and they have plenty of excuses not to—others are worse, God will forgive, at least they haven’t murdered anyone, repenting is a work but they’re saved by grace, they have some pre-existing arrangement worked out, etc. Somehow or another they figure they can ignore the gospel and aren’t imperiled by doing so.
In the case of some Christians, they have an entirely different idea of what “gospel” means. To them, “gospel” doesn’t mean the Kingdom of God is coming. “Gospel” means “Jesus has died for my sins, and if I believe in Him, I’ll have eternal life with Him in heaven.”
Now, while it’s true that Jesus saves us from sin, (Rv 1.5) for our sins, and while it’s true that those who believe in Him get eternal life, (Jn 3.16) that’s not what Jesus called the gospel. So where’d this other definition come from?
It actually comes from the assumption that this is what Paul was writing about in his letters when he wrote “gospel.” Paul used the word a lot when he was writing about the message Jesus had entrusted him. But Paul made a distinction between salvation and the gospel:
God saved us and called us to live a holy life. He did this, not because we deserved it, but because that was his plan from before the beginning of time—to show us his grace through Christ Jesus. And now he has made all of this plain to us by the appearing of Christ Jesus, our Savior. He broke the power of death and illuminated the way to life and immortality through the Good News. And God chose me to be a preacher, an apostle, and a teacher of this Good News.
2Ti 1.9ƒƒ NLT
Jesus showed the way to life and immortality via the Good News—meaning that life and immortality, and the gospel, are two different things.
Evangelists believe when they’re telling people how to turn to God and be saved, they’re “preaching the gospel.” And they sorta are. Turning to God is part of the gospel; the reason we repent of our sins, like Jesus told us to, is because we’re turning to God. But turning to God is the first step. Salvation is the first step. It’s only the starting point on the journey. The journey—the Kingdom of God, and living in it and being a part of it—is the real good news. The gospel is greater and deeper and more profound than just turning to Jesus. It’s the Kingdom.
Now as to what the Kingdom is—or, at least, what it’s like—we have to continue with the teachings of Jesus.