And my speech and my preaching were not with persuasive words of human wisdom, but in demonstration of the Spirit and of power

1 Corinthians 2:4
And my speech and my preaching were not with persuasive words of human wisdom, but in demonstration of the Spirit and of power.

Paul wants his reader to understand that  it should not be his words and skills as a preacher and speaker to turn people to Yshua. That also holds true for any of the well gifted preachers. They should always divert the glory back to Yshua. It is God, through the Holy Spirit, who moves people's hearts to true conversion into followers of Yshua. We must not rely on any particular preacher for our salvation.