The books of Matthew, Mark and Luke all record that Jesus' baptism by John the Baptist and Jesus' temptation in the wilderness were followed by His earthly ministry. Each of the books then tell us about the events and work of that ministry. From the beginning to the end of Jesus' earthly ministry, His actions repeatedly and consistently involved the preaching of the gospel.
Matthew said, "Now Jesus went about all Galilee, teaching in their synagogues, preaching the gospel of the kingdom..." (Matt. 4:23). "And Jesus went about all the cities and villages, teaching in their synagogues, preaching the gospel of the kingdom..." (Matt. 9:35). The focus Jesus had in teaching the people was to introduce them to the principles of the gospel. That gospel was the means by which people were introduced to the kingdom. Hence, when we find Jesus preaching the kingdom, we know He is declaring the gospel.
Mark added, "Now after John was put in prison, Jesus came to Galilee, preaching the gospel of the kingdom of God, and saying, 'The time is fulfilled, and the kingdom of God is at hand. Repent, and believe in the gospel'" (Mark 1:14-15). Note again the connection between the gospel and the kingdom. The preaching of the gospel of the kingdom not only informed, but through it Jesus demanded a response from the hearers of that gospel.
Luke quoted Jesus as saying, "The Spirit of the Lord is upon Me, because He has anointed Me to preach the gospel to the poor. He has sent Me to heal the brokenhearted, to preach deliverance to the captives and recovery of sight to the blind, to set at liberty those who are oppressed, to preach the acceptable year of the Lord" (Luke 4:18-19). The preaching of the gospel was connected with the blessings Christ brought. How do we know? Because Jesus made that connection between the message of the gospel and the blessing He would give. If one views the gospel's information and instruction as oppressive, he clearly has a different view of the gospel than Christ had.
How can both of these statements correctly describe the purpose Christ had in coming to this world? If we understand that the gospel of the kingdom plays a part in the salvation of the lost, the statements are easily reconciled. In the book of John, Jesus explained why His words, the gospel, are connected with salvation or eternal life. He said:
He who rejects Me, and does not receive My words, has that which judges him - the word that I have spoken will judge him in the last day. For I have not spoken on My own authority; but the Father who sent Me gave Me a command, what I should say and what I should speak. And I know that His command is eternal life. Therefore, whatever I speak, just as the Father has told Me, so I speak (John 12:48-50).
The words of Christ, His gospel, will be the standard of judgment at the end of time. That gospel represents the united will of the divine beings we know as the Father and the Son. John 14-16 shows that the Holy Spirit is also a participant in that united will since He was the one through whom the gospel was delivered by inspiration (John 14:26; 16:7-15).
If we understand that the gospel is the united will of deity, we should automatically see its importance. It is the communication of the eternal God's instructions to mortal man. It was so important that one of deity, the Son, took upon Himself the nature of humanity that He might begin the process of declaring that will to mankind.
[God] has saved us and called us with a holy calling, not according to our works, but according to His own purpose and grace which was given to us in Christ Jesus before time began, but has now been revealed by the appearing of our Savior Jesus Christ, who has abolished death and brought life and immortality to light through the gospel (2 Tim. 1:8-9).
Since God calls us to salvation through the gospel, He demands that we respect the pattern laid down within that gospel regarding how we may be saved by His grace. Paul confirms this by saying, "Hold fast the pattern of sound words which you have heard from me, in faith and love which are in Christ Jesus" (2 Tim. 1:13).