1 Corinthians 2:1

Κἀγὼ ἐλθὼν πρὸς ὑμᾶς, ἀδελφοί, ἦλθον οὐ καθ’ ὑπεροχὴν λόγου ἢ σοφίας καταγγέλλων ὑμῖν τὸ μαρτύριον τοῦ Θεοῦ.

And I, when I came to you, brothers (ἀδελφοί; adelphoi), did not come proclaiming to you the testimony (marturion; μαρτύριον) of God with excellency (hyperochēn; ὑπεροχὴν) of speech (λόγου; logou) or wisdom (sophias; σοφίας).

Paul is clear in this verse that he did not come and proclaim the gospel of God with eloquence of his speech or wisdom. The testimony of God was not proclaimed through Paul's eloquence of speech or wisdom but rather the gospel of God itself, though may sound foolish to those who are perishing, is actually the wisdom of God for salvation of many souls.

Paul gives answers to the church in Corinth in the next verse that what he came with, however, is the knowledge of Jesus Christ, our Lord, and Him crucified on the cross. This is the essence of the gospel itself. Jesus Christ and Him crucified. The most important knowledge to Paul at the time when he visited Corinth was not how he could sound eloquent or wise, but rather the demonstration of the power of the gospel of God in the message proclaimed, namely, the good news, that Jesus Christ, the Son of God, died on the cross for our sins, for our salvation.