In several instances, Jesus is proclaiming the "gospel of the kingdom" (Matt 4:23; 9:35; 24:14; Mark 1:15; Luke 16:16). What gospel is Jesus speaking of, and how does repentance work while He is alive on earth?

Jesus was going throughout all Galilee, teaching in their synagogues and proclaiming the gospel of the kingdom, and healing every kind of disease and every kind of sickness among the people. The news about Him spread throughout all Syria; and they brought to Him all who were ill, those suffering with various diseases and pains, demoniacs, epileptics, paralytics; and He healed them. Large crowds followed Him from Galilee and the Decapolis and Jerusalem and Judea and from beyond the Jordan. (Matt 4:23-25)

As they were going out, a mute, demon-possessed man was brought to Him. After the demon was cast out, the mute man spoke; and the crowds were amazed, and were saying, "Nothing like this has ever been seen in Israel." But the Pharisees were saying, "He casts out the demons by the ruler of the demons." Jesus was going through all the cities and villages, teaching in their synagogues and proclaiming the gospel of the kingdom, and healing every kind of disease and every kind of sickness. Seeing the people, He felt compassion for them, because they were distressed and dispirited like sheep without a shepherd. (Matt 9:32-36)

Now after John had been taken into custody, Jesus came into Galilee, preaching the gospel 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)

The English noun "gospel" is translated from the Greek noun "euangelion." Classical usage of euangelion was typically in the context of a messenger who brings news that causes joy (i.e. a message of victory - military, political, personal). There were two main uses of euangelion:

1) it referred to the message itself, which Greeks often viewed as a gift of the gods.

2) it referred to the reward received by the messenger of good news; good news brought relief or joy which people celebrated with a reward.

When Jewish scholars translated the Old Testament into Greek (Septuagint), "euangelion" was used to translate the Hebrew noun "beśōrâh." 2 Samuel 18:20-22 provides an example of how the Hebrew noun was used:

But Joab said to him, "You are not the man to carry news (beśōrâh) this day, but you shall carry news another day; however, you shall carry no news today because the king's son is dead." Then Joab said to the Cushite, "Go, tell the king what you have seen." So the Cushite bowed to Joab and ran. Now Ahimaaz the son of Zadok said once more to Joab, "But whatever happens, please let me also run after the Cushite." And Joab said, "Why would you run, my son, since you will have no reward (beśōrâh) for going?" (2 Sam 18:20-22)

The Hebrew noun "beśōrâh" did not share the same context of news as good news found in the Greek noun "euangelion." Changing slowly over time through Greek usage, "euangelion" evolved from the Hebrew context of "beśōrâh" to that of "good news." Scholars believe that when used in the context of oracles or the imperial cult, "euangelion" took on a religious meaning – accession to the throne introduces a new era, bringing peace to the world, and is the gospel for men. This good news of "euangelion," and perhaps the nature of its content, was carried through into the New Testament.

When John the Baptist was in prison, he sent his disciples to inquire of Jesus if He was the "Expected One" and Jesus replies affirmatively in the context of the gospel:

Jesus answered and said to them, "Go and report to John what you hear and see: the blind receive sight and the lame walk, the lepers are cleansed and the deaf hear, the dead are raised up, and the poor have the gospel preached to them. And blessed is he who does not take offense at Me." (Matt 11:4-6)

Jesus' message to John the Baptist was a reference to Isaiah 61:1-2 and indirectly of the event signaling the start of His ministry in Galilee where He visited a synagogue in Nazareth, read a prophetic passage from Isaiah, and proclaimed it fulfilled:

More than just the liberating consequences of the Servant completing the task of atonement (Isa 53:10-12), Jesus Christ understood the gospel included justice for God His Father.

For Jesus, who came for the "lost sheep of Israel" (Matt 15:24) whose priestly leaders distorted the Law with their oral traditions (Mark 7:3-8), the "gospel of God" (Mark 1:14-15) was His Father's New Covenant (Isa 59:21; 61:8-9, Jer 31:31-34; 32:40, Ezek 34:25-31; 36:25-28; 37:26-28). "Euangelion" was not simply good news that was all about Jesus and His saving act of atonement.

Despite their inability of keeping their covenant commitments, God made a new covenant with the nation of Israel for the sake of the holiness of His name, and in keeping with His promises to Abraham, provide the means for his descendants to inherit the Promised Land:

"Behold, days are coming," declares the LORD, "when I will make a new covenant with the house of Israel and with the house of Judah, not like the covenant which I made with their fathers in the day I took them by the hand to bring them out of the land of Egypt, My covenant which they broke, although I was a husband to them," declares the LORD. "But this is the covenant which I will make with the house of Israel after those days," declares the LORD, "I will put My law within them and on their heart I will write it; and I will be their God, and they shall be My people. (Jer 31:31-33)

"Therefore say to the house of Israel, ‘This is what the Lord God says: "It is not for your sake, house of Israel, that I am about to act, but for My holy name, which you have profaned among the nations where you went. And I will vindicate the holiness of My great name which has been profaned among the nations, which you have profaned among them. Then the nations will know that I am the Lord," declares the Lord God, "when I show Myself holy among you in their sight. For I will take you from the nations, and gather you from all the lands; and I will bring you into your own land. Then I will sprinkle clean water on you, and you will be clean; I will cleanse you from all your filthiness and from all your idols." (Ezek 36:22-25)

Just like the Mosaic Covenant, the New Covenant is all about teaching one how to be holy and the judicial process of dealing with sin. However, the New Covenant provides a new judicial process for redeeming sinners figuratively in prison for their crimes against God, and how they can avoid being repeat offenders.

God provides His only Son as the means to atone for the past, present, and future sins of an individual. Jesus introduces the idea of His life being a "ransom" for the purpose of redeeming people (Matt 20:28; Mark 10:45; 1 Tim 2:3-6).

For those obedient to the New Covenant, God will give a new heart and put a new spirit within them and free them from the desire to be disobedient to God.

Jesus' holistic view of the "gospel of God" is the basis for His appeal to repent, because there will be judgment for sin.

From that time Jesus began to preach and say, "Repent, for the kingdom of heaven is at hand." (Matt 4:17)

And He said to them, "Wherever you enter a house, stay there until you leave town. Any place that does not receive you or listen to you, as you go out from there, shake the dust off the soles of your feet for a testimony against them." They went out and preached that men should repent. (Mark 6:10-12)

"The Law and the Prophets were proclaimed until John; since that time the gospel of the kingdom of God has been preached, and everyone is forcing his way into it. But it is easier for heaven and earth to pass away than for one stroke of a letter of the Law to fail." (Luke 16:16-17)

Many false prophets will arise and will mislead many. Because lawlessness is increased, most people's love will grow cold. But the one who endures to the end, he will be saved. This gospel of the kingdom shall be preached in the whole world as a testimony to all the nations, and then the end will come. "Therefore when you see the abomination of desolation which was spoken of through Daniel the prophet, standing in the holy place (let the reader understand), then those who are in Judea must flee to the mountains. (Matt 24:11-16)

While God was no longer bound to the Mosaic Covenant, repenting Jews could still live by the Law and atone for their sins; the New Covenant did not come into view until the crucifixion of Jesus Christ.

In contrast to Jesus Christ, the apostle Paul presents the gospel with a focus on His work of atonement; the good news is salvation through Jesus Christ. For Paul, the good news included Jesus Christ's death, process of atonement, and validation by His resurrection. Paul's frequent use of "euangelion" without qualification to describe the nature of its content indicated a widespread understanding of its meaning; everyone already knew what the good news was and "euangelion" was used as an unqualified noun.

Paul, a bond-servant of Christ Jesus, called as an apostle, set apart for the gospel of God, which He promised beforehand through His prophets in the holy Scriptures, concerning His Son, who was born of a descendant of David according to the flesh, who was declared the Son of God with power by the resurrection from the dead, according to the Spirit of holiness, Jesus Christ our Lord, through whom we have received grace and apostleship to bring about the obedience of faith among all the Gentiles for His name's sake, among whom you also are the called of Jesus Christ; (Rom 1:1-6)

But what does it say? "The word is near you, in your mouth and in your heart"—that is, the word of faith which we are preaching, that if you confess with your mouth Jesus as Lord, and believe in your heart that God raised Him from the dead, you will be saved; for with the heart a person believes, resulting in righteousness, and with the mouth he confesses, resulting in salvation. For the Scripture says, "Whoever believes in Him will not be disappointed." For there is no distinction between Jew and Greek; for the same Lord is Lord of all, abounding in riches for all who call on Him; for "Whoever will call on the name of the Lord will be saved." How then will they call on Him in whom they have not believed? How will they believe in Him whom they have not heard? And how will they hear without a preacher? How will they preach unless they are sent? Just as it is written, "How beautiful are the feet of those who bring good news of good things!" However, they did not all heed the good news; for Isaiah says, "Lord, who has believed our report?" So faith comes from hearing, and hearing by the word of Christ. (Rom 10:8-17)

For Christ did not send me to baptize, but to preach the gospel, not in cleverness of speech, so that the cross of Christ would not be made void. For the word of the cross is foolishness to those who are perishing, but to us who are being saved it is the power of God. For it is written,
I will destroy the wisdom of the wise,
And the cleverness of the clever I will set aside." (1 Cor 1:18-19)

"Euangelion," news that brings joy, almost becomes synonymous with Jesus Christ, and this becomes the basis of recognizing the books Matthew, Mark, Luke, and John as the gospel according to those respective authors.

The beginning of the gospel of Jesus Christ, the Son of God. (Mark 1:1)

For God, whom I serve in my spirit in the preaching of the gospel of His Son, is my witness as to how unceasingly I make mention of you, (Rom 1:9)

And even if our gospel is veiled, it is veiled to those who are perishing, in whose case the god of this world has blinded the minds of the unbelieving so that they might not see the light of the gospel of the glory of Christ, who is the image of God. (2 Cor 4:3-4)