Repent, for the Kingdom of heaven has come near" (Matthew 3:2; 4:17).
Repent is a word that can conjure up the image of a heavy-handed master commanding his subjects to do as he says. Maybe that's because we're used to seeing "repent" followed by "submit." You get the idea, "Repent and submit!" It sounds heavy-handed. But the biblical use of the word repent, transliterated from the Greek as metanoeō, refers to "a change of mind for the better," especially as it pertains to a purpose they've formed or something they've done. 
The idea of repentance isn't foreign to Christians, yet it doesn't get the emphasis today that it did during Jesus' earthly ministry. In fact, repentance was at the core of Jesus' message and his predecessor, John the Baptist. Both proclaimed, "Repent, for the Kingdom of heaven has come near." Jesus and John had the same message of repentance, emphasizing why people should repent. It was because the kingdom of heaven was near, and pending judgment was closer now than ever before. Yet their messages targeted different aspects of repentance. John's message focused on the external actions resulting from repentance, while Jesus' message focused on the internal action necessary to sustain it.
What Shall We Do?
The passage in Luke 3 gives us a clear picture of John's ministry emphasis. John was going about the regions of the Jordan River proclaiming a baptism of repentance for the forgiveness of sins (v. 3). People were coming to him to be baptized as a sign of their desire to be forgiven. When religious leaders came to witness what was happening, John yelled out to them, "You brood of vipers! Who warned you to flee from the wrath to come? Bear fruit in keeping with repentance." His warning to them was stern. Only actions resulting from repentance would keep them from the flames. As John said, "Every tree therefore that does not produce good fruit will be cut down and thrown into the fire" (Matthew 3:10).
After John's interaction with the religious leaders, those who heard him asked, "What shall we do?" He responded by saying those who possessed two tunics should share one with someone who had none. Tax collectors were to collect no more than what they were authorized to. And soldiers were told not to extort money by threats or lies, being content with their wages. He instructed them to do what was right and stop doing what was wrong. He did this to instill in them remorse and desire. They needed to regret the actions that showed them to be greedy, dishonest, and ruthless and repent toward actions that showed them to be charitable, honest, and merciful.
When asked by the crowd, "What shall we do?" John's response was to do what is ethically acceptable to God. He provided clear actions which reflected good moral beliefs. That's what we mean by ethics. Ethics are the standard of our actions that reveal our moral beliefs. If one believes that it's wrong to be greedy, they'll operate with an ethical standard of never using their power or position to extort money from others. What was missing in John’s message was how to overcome sin, which stood as the biggest obstacle to living an ethical life. John pointed to the answer when he said, “Behold, the Lamb of God, who takes away the sin of the world!" (John 1:29).
Set Free to Live Ethically
There is no adequate way to summarize Jesus' ministry on earth, but his inaugural address in Luke 4 provides some help. After Jesus took the scroll in the synagogue, he turned to Isaiah and read:
The Spirit of the Lord is upon me because he has anointed me to proclaim good news to the poor. He has sent me to proclaim liberty to the captives and recovering of sight to the blind, to set at liberty those who are oppressed, to proclaim the year of the Lord's favor (Luke 4:18-19).
While one could take these words as ethically inclined, the truth is they are spiritual in nature. Jesus' message wasn't about alleviating poverty, freeing the imprisoned, healing physical blindness, or ending physical oppression. It was about good news for those who were poor in spirit and mourned over their captivity to sin. The "good news," or the gospel that Jesus proclaimed, was that He had come to set humanity free from sin's oppression, removing its death grip on their beliefs and actions.
John the Baptist's message convicted people who needed to hear that their actions opposed God's will. John called them to account for those actions, and their hearts were moved to repent. They were moved to reflect and rethink what they were doing and revise their actions once they knew what to do. Jesus followed John's message with His own, proclaiming that He was the only way for them to continue doing what was good and right. The continued revision of their actions was only possible through Christ. That's the message that the Apostle Paul took up as his own.
The book of Acts records Paul saying he did "not shrink back" from testifying about "repentance toward God and faith in our Lord Jesus Christ." In the same speech, he later says: "I did not shrink back from declaring to you the whole will of God" (Acts 20:21,25). When speaking of "repentance toward God," he's saying that we should measure our beliefs and actions against the commands given to us by God. And we're not free to pick and choose which commands we'll follow. We must submit to the "whole will of God." But if we were left to fight this battle for ourselves, it would be a losing one.
Sin is always present, persuading us to trust in ourselves, choose our own standards of right and wrong, and follow them, even if they're against God's will. That's the essence of willful sin. But when we compare our ethical standards against God's, we should be moved to repent of our standard and choose to follow God's. That's where faith comes in. As we trust Jesus at His word and act upon that belief, we discover the power of His sovereignty over all things when he engineers circumstances and outcomes to prove His trustworthiness. While the immediate circumstances we experience may not be pleasant, the eventual outcome delivers the things we long for in life, primarily doing that which is pleasing to God. God is even the initiator of the entire process since it is Holy Spirit who compels us to repent toward God and place our faith in Jesus Christ. And all of that is truly good news!