I Corinthians 3:21 Therefore let no man glory in men. For all things are yours;
The Lord Jesus is to be our glory. He is the One we are to boast in and on.
We get so hung up on personalities. We brag because we know someone. This early church was personality crazy. They had formed cliques around their heroes. I am of Paul, and others were of Apollos. This attitude does not come from the heart of God, nor is it the attitude He wanted them to have.
Then it seems that many today want to be sure to be highly rated among their brothers. There is not much of the idea that we are servants but rather that we should be served.
Here we have a command. Do not glory in people. Glory in the Lord. It is God that does the real work. Our glorying or boasting is foolish. It is like the hammer boasting about what it did or can do. The hammer is nothing without the hand of the knowledgable and capable carpenter. The tool can not boast of what the craftsman can do.