1 Corinthians 1:10-14, 16-18 NET I urge you, brothers and sisters, by the name of our Lord Jesus Christ, to agree together, to end your divisions, and to be united by the same mind and purpose. For members of Chloe’s household have made it clear to me, my brothers and sisters, that there are quarrels among you. Now I mean this, that each of you is saying, “I am with Paul,” or “I am with Apollos,” or “I am with Cephas,” or “I am with Christ.” Is Christ divided? Paul wasn’t crucified for you, was he? Or were you in fact baptized in the name of Paul? I thank God that I did not baptize any of you except Crispus and Gaius, (I also baptized the household of Stephanus. Otherwise, I do not remember whether I baptized anyone else.) For Christ did not send me to baptize, but to preach the gospel – and not with clever speech, so that the cross of Christ would not become useless.
For the message about the cross is foolishness to those who are perishing, but to us who are being saved it is the power of God.
The ideas in that passage are that each person was boasting about the superiority of their teachings, when all of them were in fact disciples of the same teaching, which was again, an "inferior“ (foolish) teaching. They had absolutely no grounds for boasting, either in terms of uniqueness or superiority.
Baptism is the equivalent of recognising a person can now have table fellowship with God's People. That status must be maintained, just as the observant Jew needed to maintain his clean status and act to rectify any impurity, whether caused accidentally or through carelessness .
1 Corinthians 5:11New International Version (©1984) But now I am writing you that you must not associate with anyone who calls himself a brother but is sexually immoral or greedy, an idolater or a slanderer, a drunkard or a swindler. With such a man do not even eat.
Matthew 18:17 NET If he refuses to listen to them, tell it to the church. If he refuses to listen to the church, treat him like a Gentile or a tax collector.
Acts 8:13, 20-23 NET Even Simon himself believed, and after he was baptized, he stayed close to Philip constantly, and when he saw the signs and great miracles that were occurring, he was amazed.
But Peter said to him, “May your silver perish with you, because you thought you could acquire God’s gift with money! You have no share or part in this matter because your heart is not right before God! Therefore repent of this wickedness of yours, and pray to the Lord that he may perhaps forgive you for the intent of your heart. For I see that you are bitterly envious and in bondage to sin.”
In that sense, baptism is an acknowledgement of the suitability of the candidate. The Ethiopian eunuch's request was based on that reasoning.
The Corinthian church had distorted that teaching.