Trinity Evangelical Lutheran Church, Creston, Iowa;
And I, when I came to you, brothers, did not come proclaiming to you the testimony of God with lofty speech or wisdom. For I decided to know nothing among you except Jesus Christ and him crucified. And I was with you in weakness and in fear and much trembling, and my speech and my message were not in plausible words of wisdom, but in demonstration of the Spirit and of power, that your faith might not rest in the wisdom of men but in the power of God. Yet among the mature we do impart wisdom, although it is not a wisdom of this age or of the rulers of this age, who are doomed to pass away. But we impart a secret and hidden wisdom of God, which God decreed before the ages for our glory. None of the rulers of this age understood this, for if they had, they would not have crucified the Lord of glory. But, as it is written, “What no eye has seen, nor ear heard, nor the heart of man imagined, what God has prepared for those who love him”— these things God has revealed to us through the Spirit. For the Spirit searches everything, even the depths of God. For who knows a person’s thoughts except the spirit of that person, which is in him? So also no one comprehends the thoughts of God except the Spirit of God. Now we have received not the spirit of the world, but the Spirit who is from God, that we might understand the things freely given us by God. And we impart this in words not taught by human wisdom but taught by the Spirit, interpreting spiritual truths to those who are spiritual. The natural person does not accept the things of the Spirit of God, for they are folly to him, and he is not able to understand them because they are spiritually discerned. The spiritual person judges all things, but is himself to be judged by no one. “For who has understood the mind of the Lord so as to instruct him?” But we have the mind of Christ. ” (1 Corinthians 2:1–16, ESV)
Grace and peace to you from our Lord and Savior, Jesus Christ.
It is difficult for a pastor to talk about Christian maturity. The problem, for a pastor, is this: many of you will think you are spiritually mature. Your first thoughts on this topic are to think that you’ve obtained some spiritual level higher than your brothers and sisters in Christ. You’ll think you’ve put away certain sins evidenced by the fact that you no longer struggle with them. You joyfully participate in the activities of the church, give your fair share to the budget, say good things about your pastor, and pray through the whole prayer list in the bulletin. You’ve weathered the storms of church politics, pastors with problems, and a long vacancy. You look at the blessings of your church, life, family, work, security as proof that you’ve been blessed by God because you are spiritual, because you have stood firm, because you have run the race and won. Obviously those who struggle to give anything to the church with joy haven’t reached that level of maturity. Obviously those who struggle with sexual temptation haven’t reached that level of spiritual maturity. Obviously those who… how does the saying go? “I don’t smoke, drink or chew and I don’t date girls who do.” If I’ve heard it once I’ve heard it a million times. “Before I came to the Lord, I insert your favorite sin here, but now I don’t even have the desire to insert your favorite sin.” It just all sounds vaguely familiar.
“Two men went up into the temple to pray, one a Pharisee and the other a tax collector. The Pharisee, standing by himself, prayed thus: ‘God, I thank you that I am not like other men, extortioners, unjust, adulterers, or even like this tax collector. ” (Luke 18:10–11, ESV)
You see, the Pharisee thought he was spiritually mature. He’d conquered all those sins. The tax collector hadn’t. Obviously, he was spiritually lacking, immature. Maybe if he just worked a little bit harder, attended church on a more regular basis, dropped just a bit more in the collection plate, sat closer to the front of the church, worked on the youth board, maybe then God would clear all those sins out of his life.
You see, that’s the problem with talking about spiritual maturity. Whenever we, sinful human beings, begin to think about growing up in the faith we naturally turn to ourselves. We look to what we must do to make it all happen. And then we boast in our accomplishments and congratulate ourselves on our spiritual maturity.
Paul calls this the “spirit of the world.” And it had invaded the church at Corinth. There were divisions in the church. Some claimed to be more mature because they followed Paul or Apollos. Some thought that they were spiritually mature so they could do whatever they wanted (one man even married his father’s wife!). Paul’s letter to them points out these errors in thinking. He doesn’t go easy on them either, calling for excommunication for open unrepentant sin. It is chilling, “Hand this one over to Satan.” (5:5) he says. For a Christian to live according to the “spirit of the world” is a very dangerous place to be. For a Christian to live in unrepentant sin is to be on the path to denying Jesus Christ. Our own confessions say, But those who walk according to the flesh [Galatians 5:19–21] retain neither faith nor righteousness. 
Paul’s warning comes from a firm hand, as does my pastoral warning to you. Beware of your sin, beware of your pride, and beware of your natural tendency to put others in their place while ignoring the log in your own eye. There is only one thing that can be done with a sinner. He must die. Shall I say it even stronger? There is only one thing that can be done with a sinner. He must suffer hell’s punishment. So beware of your sin, Christian. It can only lead you to one place, eternal separation from the Holy God.
Now, dear Christian, I would be neglecting my job as your pastor, if on the heels of that strong law I would direct you to yourself as a solution. “Try harder!” “Do these ten biblical principal and you’ll remove temptation to sin.” “Read your bible every day and God will make you strong enough to overcome.” “You can be victorious if you pray everyday.” “Of all the things Jesus talked about he talked most about money. The bible tells you more about managing your money than anything else!” These are actually more of the same. These are reflections of the wisdom of the world creeping to the church. In fact, if I preached these kinds of sermons you’d soon be nodding your head in agreement. “Yea, that’s what I need some practical stuff to make a difference in my life.” But that’s not Paul’s solution to the problems of spiritual immaturity in the Corinthian church. What does he say?
And I, when I came to you, brothers, did not come proclaiming to you the testimony of God with lofty speech or wisdom. For I decided to know nothing among you except Jesus Christ and him crucified. (2:1)
In fact, this is exactly what St. Paul calls spiritual maturity. It is seeing the foolishness of the cross of Jesus as the solution over and against the wisdom of the world. Not our doing anything. Not our working out our own way out of sin. But clinging to the cross, to Jesus and Jesus Christ crucified as our solution for sin. Spiritual maturity is here at the font, here at the altar, here in the pew when Jesus’ forgiveness from the cross is poured out on you and spoken into your ears. The two most important words you will ever hear in this church are “for you.” This is the Spirit of God at work against the spirit of the world.
Now we have received not the spirit of the world, but the Spirit who is from God, that we might understand the things freely given us by God. (2:12)
So what are the things freely given? The forgiveness of sins won by Jesus on the cross, life and salvation. For as the Catechism says, For where there is forgiveness of sins, there is also life and salvation.
I have been crucified with Christ. It is no longer I who live, but Christ who lives in me. And the life I now live in the flesh I live by faith in the Son of God, who loved me and gave himself for me. ” (Galatians 2:20, ESV)
But far be it from me to boast except in the cross of our Lord Jesus Christ, by which the world has been crucified to me, and I to the world. ” (Galatians 6:14, ESV)
So there it is spiritual maturity as defined by God’s Word. It is not my victory over sin; my improving life. It’s not my best life now or my pursuing the purpose God give me in my heart. It is not thinking that there is something I can do to deal with my own sin. It is seeing that my sin is over my head. It is seeing the absolute danger of my sin and fearing the eternal consequences of it. It is also seeing that God has done what it necessary to remove it. It is seeing Jesus Christ bleeding and dying on the cross as the only answer. It is clinging, in faith, to Jesus as my savior and boasting in Jesus Christ crucified for me. Amen.
The peace of God that passes all understanding, keep your hearts and minds in Christ Jesus. Amen.
 Concordia : The Lutheran Confessions. 2005 (Edited by Paul Timothy McCain) (135). St. Louis, MO: Concordia Publishing House.
 Concordia : The Lutheran Confessions. 2005 (Edited by Paul Timothy McCain) (343). St. Louis, MO: Concordia Publishing House.