And my speech and my preaching were not with persuasive words

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

Our preaching of the gospel to others need to come from our own knowing that the gospel is real. This is not just knowledge but a deep knowing of the reality. We can only do that when we sincerely believe of its truth and is living it out in our lives. Then human wisdom and presentation of the words itself is secondary because the power of God would take centre-stage when we preach from our own beliefs.

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.