When the Apostle Paul wrote his first epistle to the Church in Corinth, he addressed their quarreling and arguing amongst themselves and their putting more faith in their human leaders and role models than they were putting in Christ Himself.
Now I exhort you, brethren, by the name of our Lord Jesus Christ, that you all agree and that there be no divisions among you, but that you be made complete in the same mind and in the same judgment. For I have been informed concerning you, my brethren, by Chloe's people, that there are quarrels among you. Now I mean this, that each one of you is saying, "I am of Paul," and "I of Apollos," and "I of Cephas," and "I of Christ." Has Christ been divided? Paul was not crucified for you, was he? Or were you baptized in the name of Paul? (1 Corinthians 1:10-13)
Paul addresses some other important issues, but he is distressed at the lack of unity and purpose that the collective people of God ("the church") in Corinth are experiencing while they argue about non-eternal matters and boast in the flesh. As the Apostle begins to wind down this same letter, he reminds them of the importance of the gospel:
Now I make known to you, brethren, the gospel which I preached to you, which also you received, in which also you stand, by which also you are saved, if you hold fast the word which I preached to you, unless you believed in vain. For I delivered to you as of first importance what I also received, that Christ died for our sins according to the Scriptures, and that He was buried, and that He was raised on the third day according to the Scriptures... (1 Corinthians 15:1-4, emphasis added)
After dealing with various issues and problems, Paul points these believers to the most important truth of Scripture: the gospel message itself, which Paul received directly from the risen Lord Jesus. This glorious gospel declares that Jesus is the promised Messiah from the Scriptures who came to fulfill God's promises revealed through what we call the Old Testament scriptures, that He died for our sins according to God's predetermined plan (e.g. Isaiah 52:13-53:12), that He was buried (e.g. Isaiah 53:9), and that He was resurrected on the third day (Isaiah 53:10) fulfilling God's promises and demonstrating to the world that Jesus, whom we crucified, God has made both Lord and Christ (Acts 17:30-31, Romans 1:4). This glorious truth is of first importance, and is the basis for the unity in the church - whether in Corinth or anywhere else!
Instead of fighting about lesser things, Paul is encouraging these followers of Jesus to refocus their attention on the gospel and the implications of this truth, instead of debating which preacher is best or whatever else!
So what are the implications of the gospel?
Paul states plainly that the resurrection of Jesus demonstrates the truth of Christianity and the reality of the coming resurrection for all people at the Judgment (1 Corinthians 15:12-28). Jesus is the appointed King of the universe and He will reign until all of His enemies are put under His feet (1 Corinthians 15:25-27), and it is only through repentance and faith that anyone is able to participate in His sacrificial death for the penalty of their own sin.
Think about this for a minute.
Really, think about it.
Is there anyone you know who is not "in Christ"?
If so, what does this mean for them?
If you are a follower of Jesus, then His resurrection proves the truth of your salvation. On the flip side, it proves the truth of the condemnation that is upon all who do not believe.
He who believes in the Son has eternal life; but he who does not obey the Son will not see life, but the wrath of God abides on him. (John 3:36)
Paul cuts straight to the heart of the matter in verse 34:
Become sober-minded as you ought, and stop sinning; for some have no knowledge of God. I speak this to your shame. (1 Corinthians 15:34)
According to Paul, these believers need to dwell soberly on the truth of their salvation in Christ and the condemnation that is upon the world and stop sinning. Stop paying attention to unimportant matters. Stop bragging about yourself and your favorite teacher/leader. Stop putting your eyes on the world and the things that are fading away.
Stop sinning. Seriously.
But why does Paul say we need to be sober minded and stop sinning? Because some have no knowledge of God. We have received the revelation of God (remember 1 Corinthians 15:1-2), the message by which we can pass from death into life and which is the power of God unto salvation for all who believe (Romans 1:16-19). If this is true (and it is!), then Paul says the mere fact that there are some in Corinth who are unaware of this truth due to the church's failure to proclaim it boldly is something that they ought to be ashamed of.
Do you agree with Paul?
Do you think it's shameful that the church hides the light of the gospel under a basket and fights amongst themselves on doctrines and matters of theology that are of lesser importance than the gospel, which is of first importance?
Do you agree that it's shameful that we who know the truth are not willing to pay the cost to bring this message to those who are lost and perishing?
Do you not know that it is required of servants of Christ that we be found trustworthy in our stewardship of the gospel?
Who do you know who has no knowledge of God? What are you doing to put them in mind of the coming judgment and the command from the risen King for all men everywhere to repent (Acts 17:30-31)?
If the answer is "nothing", then Paul suggests that we, too, should be ashamed.
Fortunately, God is pleased in His grace to give us further opportunities to be found faithful and trustworthy with His gospel - even if we've been negligent in the past!
The sting of death is sin, and the power of sin is the law; but thanks be to God, who gives us the victory through our Lord Jesus Christ. Therefore, my beloved brethren, be steadfast, immovable, always abounding in the work of the Lord, knowing that your toil is not in vain in the Lord. (1 Corinthians 15:56-58)
God is able to use His church for the praise and glory of His name (Ephesians 3:20-21) and He has made us adequate for this task of proclaiming His glory and goodness to the world (2 Corinthians 3:4-6, 1 Peter 3:9-10). Therefore, let us no longer live for ourselves, but live for Him (Galatians 2:20) in the strength He provides, knowing that He is able to accomplish what He has begun (Philippians 1:6)!
Get equipped. Obey your King. Glorify your God.