What is the gospel? If you don't even know what the gospel is, you shouldn't say you're preaching the gospel.
The Church of God will properly tell you what the Gospel is.

1. The New Covenant of the Gospel

Colossians 1:23 This gospel has been preached to every creature under heaven, and I, Paul, became a minister of this gospel.

2 Corinthians 3:6 He has also satisfied us to be servants of the new covenant...

Apostle Paul called us ministers of the gospel in Colossians, but he called us ministers of the new covenant in 2 Corinthians.
A worker of the gospel means a worker of the new covenant.In other words, the gospel is the new covenant.

2. Passover is the core of the new covenant

Luke 22:20 In the same way he took the cup after supper, saying, This cup is the new covenant in my blood, which is poured out for you.

The core of the new covenant is the Passover. The Passover is a covenant established by the blood of Christ.
Therefore, to put the gospel simply, it is the New Covenant Passover.
The gospel preached by Apostle Paul is the New Covenant Passover. The reason Christ shed His blood on the cross was to establish the Passover of the new covenant. The Passover of the new covenant is the feast of Christ's death and love.
This is the gospel.
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3. The Gospel that Jesus preached

Matthew 4:23 Jesus went throughout Galilee, teaching in their synagogues and preaching the good news of the kingdom.

The gospel of the new covenant that Jesus preached is the Passover of the new covenant.
Those who claim to believe in Jesus but do not keep the New Covenant Passover are not believers in Jesus.
A true believer in Christ must keep the Passover.

​The Church of God is the true church that believes in Christ correctly. The reason is that the Church of God is the only one that keeps the Passover. The church that preaches the gospel of the kingdom is the Church of God.