Thank you for asking. Here is a scripture to confirm what Jesus"s Definition of the Gospel is.
Matt 9:35 And Jesus went about all the cities and villages, teaching in their synagogues, and preaching the
gospel of the kingdom, and healing every sickness and every disease among the people.
Ephesians 3:1 - For this reason I, Paul, the prisoner of Christ Jesus for you Gentiles— 2 if indeed you have heard of the
dispensation of the grace of God which was given to me for you, 3
how that by revelation He made known to me the mystery (as I have briefly written already, 4 by which, when you read, you may understand my knowledge in the mystery of Christ), 5
which in other ages was not made known to the sons of men, as it has now been revealed by the Spirit to His holy apostles and prophets: 6 that
the Gentiles should be fellow heirs, of the same body, and partakers of His promise in Christ through the gospel, 7 of which I became a minister according to the gift of the grace of God given to me by the effective working of His power. 8 To me, who am less than the least of all the saints, this grace was given, that I should preach among the Gentiles the unsearchable riches of Christ, 9 and to make all see what is the fellowship of the
mystery, which from the beginning of the ages has been hidden in God who created all things through Jesus Christ.
That was not part of the gospel which the twelve, John the Baptist, and Jesus Christ were preaching. Yet, they were still preaching the
gospel of the kingdom to Israel.
Jesus Christ sent the twelve to preach
only to Israel. Matthew 10:5 - These twelve Jesus sent out and commanded them, saying:
“Do not go into the way of the Gentiles, and do not enter a city of the Samaritans. 6
But go rather to the lost sheep of the house of Israel. 7 And as you go,
preach, saying, ‘The kingdom of heaven is at hand.’ The disciples were specifically told to go only to the people of Israel, and they were not preaching anything about the death, burial, and resurrection of Christ or that the Gentiles should be fellow heirs, of the same body, and partakers of His promise in Christ through the gospel.
In Matthew 16:15, Jesus Christ asked His disciples, “But who do you say that I am?” 16 Simon Peter answered and said,
“You are the Christ, the Son of the living God.” 17 Jesus answered and said to him, “Blessed are you, Simon Bar-Jonah, for flesh and blood has not revealed this to you, but My Father who is in heaven.
Now Peter had no clue that Jesus Christ would be crucified and resurrected, although he did believe that Jesus was the Messiah. This is obvious when, only moments later,
Peter rebukes Jesus Christ for saying he will be killed, and be raised again the third day" (Matthew 16:21). In verse 22,
"..Peter took him and began to rebuke him, saying, “Far be it from You, Lord; this shall not happen to You!”
Before his death, Jesus told the twelve that he had to die and that he would rise on the third day. Looking back upon this passage we see this as Jesus speaking of an event that would change the history of the world. However, it is unquestionable that the disciples were
ignorant of its meaning.
“Then he took unto him the twelve, and said unto them, Behold, we go up to Jerusalem,…
And they shall scourge him, and put him to death: and the third day he shall rise again. And
they understood none of these things: and this saying was hid from them, neither knew they the things which were spoken. – Luke 18:31-34. hmm... that's strange if the gospel that came through a revelation of Jesus Christ to Paul (Galatians 1:11-12) and
was a mystery prior to that has the same content as the gospel of the kingdom. *This is where we need to RIGHTLY DIVIDE THE WORD OF TRUTH.
After his crucifixion, instead of anxiously waiting his resurrection, the apostles were still ignorant, disheartened at the death of their redeemer, and did not even at first believe the testimony of his resurrection (Mark 16:14, Luke 24:19-24).
It was not until after his resurrection that Jesus appeared to the apostles and
opened their understanding (Luke 24:44-47).
*In this age, there is a distinctive element to the content of the gospel which is called "the mystery of the gospel" (see Ephesians 6:19 and compare with Colossians 1:26-27; 4:3). This new revelation is that the Gentiles are fellow-heirs and fellow-members of the body, and fellow-partakers of the promise (Ephesians 3:6). Such equality, Jew and Gentile united together in one body was previously unknown. The distinctive message of the church is that Jew and Gentile alike may believe the gospel and be united together into ONE BODY (Ephesians 1:13; 1 Corinthians 12:13). *Where was this preached by the disciples before the cross?
