Some people follow a certain line of thinking in which there appears to be more than one gospel. These are supposedly spoken of in the following passages:
And he went throughout all Galilee, teaching in their synagogues and proclaiming the gospel of the kingdom and healing every disease and every affliction among the people. (Matthew 4:23)
But I do not account my life of any value nor as precious to myself, if only I may finish my course and the ministry that I received from the Lord Jesus, to testify to the gospel of the grace of God. (Acts 20:24)
Now to him who is able to strengthen you according to my gospel and the preaching of Jesus Christ, according to the revelation of the mystery that was kept secret for long ages (Romans 16:25)
Then I saw another angel flying directly overhead, with an eternal gospel to proclaim to those who dwell on earth, to every nation and tribe and language and people. (Revelation 14:6)
So some people claim that there are three different gospels (where “my gospel” (Paul speaking) is the same as “the gospel of the grace of God”, where again Paul was speaking). However, I'm going to say that there are not three gospels, but that these are three ways of speaking about the one and only true gospel. Even where it speaks of a "mystery that was kept secret", it's not speaking of a new gospel that was kept secret, but simply the greater detail of God's plan of redemption which we have through New Testament revelation.
Now, the word “gospel” means “good news”. And what is this news that is so good? It is the news that Jesus Christ has paid for our sins on the cross, and that salvation is by grace, through faith in Christ, apart from our works. Those who consider there to be three different gospels refer to the first “gospel of the kingdom” as one in which, to be saved, people had to be obedient to the Old Testament laws of God. But this wouldn't be good news at all! Nobody can be saved by obedience to the laws of God; nobody can keep God's laws perfectly. Perhaps people who hold this belief aren't too worried about that because they would be under the gospel of grace, and keeping the laws of God was somebody else's problem; namely, anyone who lived before the death and resurrection of Christ. So this idea of the “gospel of the kingdom” stems from the belief that, in the Old Testament, people were saved by obedience to the Law; and where Jesus speaks of the gospel of the kingdom, He does so at a time when this particular gospel was “in effect” - a time before Paul received his “new” gospel. But that Old Testament folk were saved through obedience to the Law is not true, and there is a vast amount of Scriptural support against that. There has only ever been one gospel, but it has been revealed gradually over time. What Adam and Eve knew of it was less than what Moses knew, and he knew less than King David, and so on. But today we know that salvation is provided through Christ's atonement on the cross. This is really just a further detail to the one gospel message; a detail which we might say was “kept secret for long ages”. The point is that no further detail ever contradicts prior revelation of the gospel message making it a “new gospel”, but rather makes a more detailed gospel.
Perhaps the most compelling Scriptural support that we only have one gospel throughout all of Biblical history is that Paul, (who is supposedly preaching a different “gospel of grace”), proves that justification is by faith apart from works by looking at how Old Testament figures were justified! Consider the following passage:
For if Abraham was justified by works [ie obedience to the law], he has something to boast about, but not before God. For what does the Scripture say? “Abraham believed God, and it was counted to him as righteousness.” (Romans 4:2-3)
Again Paul, writing in Galatians, says:
So then, those who are of faith are blessed along with Abraham, the man of faith. (Galatians 3:9)
Paul says later in that chapter explicitly that the Law never saved anybody...
For if a law had been given that could give life, then righteousness would indeed be by the law. (Galatians 3:21)
The gospel is sometimes called the “gospel of the kingdom” because it is through believing the gospel that one becomes a “citizen” of the kingdom of God. At the end of Acts it says that Paul “welcomed all who came to him, proclaiming the kingdom of God and teaching about the Lord Jesus Christ with all boldness and without hindrance.” (Acts 28:30-31). Paul’s ministry of the gospel appears to be synonymous with preaching “the kingdom”.
Now if we turn our attention to the “eternal gospel” of Revelation 14:6, we can wonder whether this is the same gospel again. Well, we can note that it was an angel who proclaimed this “eternal gospel” in Revelation 14:6. Interestingly enough, Paul has this to say in Galatians 1...
But even if we or an angel from heaven should preach to you a gospel contrary to the one we preached to you, let him be accursed. As we have said before, so now I say again: If anyone is preaching to you a gospel contrary to the one you received, let him be accursed. (Galatians 1:8-9)
Paul makes it clear – there is only one gospel. The gospel in Revelation 14:6 is summarized a few verses later as this:
Here is a call for the endurance of the saints, those who keep the commandments of God and their faith in Jesus. (Revelation 14:12)
So clearly it refers to “faith in Jesus”. But it also refers to “keeping the commandments of God.” So is this a different gospel to justification by faith alone; namely a gospel of faith plus works? No. Keeping the commandments of God is what genuine faith looks like in anyone who has ever had genuine faith, or ever will have. And this is something we will discuss tomorrow.