What I mean by "what the gospel was" is simply what Jesus (and other Torah-observant Jews of his time) thought of when he said the word gospel. Mark records the opening lines of Jesus' ministry: The time is fulfilled and the kingdom of God is near. Repent and believe the gospel! So what did he mean by this?
He couldn't have meant, of course, that I have died for your sins and risen again on the third day because he hadn't done that yet. So there must have been a gospel before the gospel--a gospel 1.0. And in order to find that, we must turn to the pages of Jesus' scriptures, the Old Testament.
Perhaps the best place to start is in Isaiah, and as instructive a passage as any comes from chapter 52.
How beautiful on the mountainsSo what is the good news? It's not the peace or the salvation--those are what flow out of the reality that lies behind the good news. The good news is simply that the God of Zion, YHWH, reigns. (Of course, I'm skipping over A LOT of stuff. But since this is a blog and not a dissertation, I'll allow it. If you want to read more on this, I highly recommend N.T. Wright's The New Testament and the People of God and Jesus and the Victory of God.) In other words, the gospel as Jesus understood it at the beginning of his ministry, was YHWH is King.
are the feet of those who bring good news,
who proclaim peace,
who bring good tidings,
who proclaim salvation,
who say to Zion,
"Your God reigns!"
That's what he meant when he walked around Israel declaring that the kingdom of God had come upon the nation. He meant that YHWH is now decisively taking his rightful place as King of all Creation. How he was doing that, and what it all meant, and what were the implications of it all is another blog (or book) for another day. But that he was doing it was apparent to Jesus. YHWH is King. That's the Gospel 1.0.