For an introduction to this series, click here.
Paul opens this chapter with a stinging condemnation of the Corinthian believers: "But I, brothers, could not address you as spiritual people, but as people of the flesh, as infants in Christ. I fed you with milk, not solid food, for you were not ready for it. And even now you are not yet ready, for you are still of the flesh. For while there is jealousy and strife among you, are you not of the flesh and behaving only in a human way? For when one says, 'I follow Paul,' and another, 'I follow Apollos,' are you not being merely human?" (3:1-4)
If you just read that in context, I cannot understand how you can come to the conclusion that carnality is a natural stage of the Christian life, but that is what I have heard preached practically all my life. Paul is very clear that the Corinthians' carnality is not normal. Now certainly there is a maturity level that comes with more experience in living the Christian life, but to say that some people are just going to be carnal and there is nothing we can do about it but try to help them grow is not helping them at all. It is just an excuse for their sin.
Anyway, apparently these divisions in the Corinthian church were very serious. The church at Corinth had a lot of problems, apparently more than any other church that ever received an epistle. I have never attended one, but I cannot imagine the mindset that some people have when they choose the name "Corinth Baptist Church" or some other denomination and the name Corinth. Why would you name your church after one that was so spiritually backward?
Paul transitions from his discussion about how we are all working toward the increase of God's kingdom to a warning about the coming judgment: "For we are God's fellow workers. You are God's field, God's building. According to the grace of God given to me, like a skilled master builder I laid a foundation, and someone else is building upon it. Let each one take care how he builds upon it. For no one can lay a foundation other than that which is laid, which is Jesus Christ. Now if anyone builds on the foundation with gold, silver, precious stones, wood, hay, straw— each one's work will become manifest, for the Day will disclose it, because it will be revealed by fire, and the fire will test what sort of work each one has done. If the work that anyone has built on the foundation survives, he will receive a reward. If anyone's work is burned up, he will suffer loss, though he himself will be saved, but only as through fire." (3:9-15)
This is a solemn warning. The judgment that we will receive as believers is not a judgment for sin, that has already been taken care of. But there is a positive judgment of what we have done. If we have served the Lord, we will have rewards added. If we do not, we will still be in heaven, but that will be it. I would also assume that the rewards will include not only the crowns that are mentioned in several places in the New Testament but also placements in Christ's millennial and eternal kingdoms. I think that is implied in Scripture, even if it is not specifically stated that way.
Paul ends the chapter with another statement about worldly wisdom and Godly wisdom: "Let no one deceive himself. If anyone among you thinks that he is wise in this age, let him become a fool that he may become wise. For the wisdom of this world is folly with God. For it is written, 'He catches the wise in their craftiness,' and again, 'The Lord knows the thoughts of the wise, that they are futile.'" (3:18-20, ESV)
Apparently this was one of the main problems of the Corinthian believers. I guess they thought they had a lot of wisdom, and they saw themselves as being better than a lot of the other churches. But Paul brings this up again and again. Natural human wisdom is admirable, but it is not an end in itself. We need to seek the Lord's wisdom in order to be truly wise.