Preaching seems to me to be at its core a presumptuous undertaking—at least if I really believe that preaching is what I claim to believe it is.
If preaching is just making a speech or sharing my opinions or delivering an address or offering an entertainment or getting up in front of people and saying something, then it is not so presumptuous. After all, I have things to say and I have the ability to say them; if I can find a venue in which to get up and say it, then more power to me. Such activity may well be filled with presumption born of ego—I presume that you care about and want to hear what I am saying—but any human being can be possessed of such ego and thus of such presumption.
But preaching is, I claim to believe, much more than speech-making or opinion-sharing or address-delivering or entertainment-offering; preaching is, I claim to believe, the proclaiming of God’s word by a human being—in my case, me—to other human beings.
I claim that in my preaching, then, I am serving as a spokesperson for God Almighty.
How presumptuous is it for me to claim that God wants me to speak for God?
How presumptuous is it for me to claim that God lets me know what I am to say for God?
How presumptuous is it for me to claim that God forgives me for what I say for God?