Paul was a scholar and an orator of the highest degree; he was not speaking here out of a deep sense of humility, but was saying that when he preached the gospel, he would veil the power of God if he impressed people with the excellency of his speech. Belief in Jesus is a miracle produced only by the effectiveness of redemption, not by impressive speech, nor by wooing and persuading, but only by the sheer unaided power of God. The creative power of redemption comes through the preaching of the gospel, but never because of the personality of the preacher.
Real and effective fasting by a preacher is not fasting from food, but fasting from eloquence, from impressive diction, and from everything else that might hinder the gospel of God being presented. The preacher is there as the representative of God— “. . . as though God were pleading through us . . .” (2 Corinthians 5:20). He is there to present the gospel of God. If it is only because of my preaching that people desire to be better, they will never get close to Jesus Christ. Anything that flatters me in my preaching of the gospel will result in making me a traitor to Jesus, and I prevent the creative power of His redemption from doing its work.
“And I, if I am lifted up. . . , will draw all peoples to Myself” (John 12:32).