I found the below anecdote from the autobiography of George Muller to be quite interesting. He recounts the first time he ever preached, and how he had no idea how to prepare a sermon, so he borrowed another preacher’s sermon and MEMORIZED the whole thing. How long was that sermon? Roughly one hour. Here’s the whole story below, with the pertinent part in bold:
This schoolmaster asked me, whether I would not preach in his parish, as the aged and infirm clergyman would be very glad of my assistance. Up to this time I had never preached, though for fifteen months past I might have done so as a student of divinity; for before Christmas 1825 I had been mercifully kept from attempting to preach, (though I wrote to my father about July that I had preached, because I knew it would please him), and after Christmas, when I knew the Lord, I refrained from doing so, because I felt that I was yet too little instructed in the things of God. The same reason ought to have still kept me from preaching; yet I thought, that, by taking a sermon, or the greater part of one, written by a spiritual man, and committing it to memory, I might benefit the people. Had I reasoned scripturally, I should have said, surely it cannot be the will of God, that I should preach in this way, if I have not enough knowledge of the Scriptures to write a sermon. Moreover, I had not enough light nor tenderness of conscience to see, that I was a deceiver in the pulpit; for every body supposes, that the sermon a man preaches is, if not entirely, at least as to the most part, his own composition.
I now set about putting a printed sermon into a suitable form, and committing it to memory. It was hard work. There is no joy in man’s own doings and choosings. It took me nearly a whole week to commit to memory such a sermon as would take up nearly an hour in repeating. I got through it, but had no enjoyment in the work. It was on August 27, 1826, at eight in the morning, in a chapel of ease, in connection with which my friend was schoolmaster.* At eleven I repeated the same sermon verbatim in the parish church. There Was one service more, in the afternoon, at which I needed not to have done any thing; for the schoolmaster might have read a printed sermon, as he used to do. But having a desire to serve the Lord, though I often knew not how to do it scripturally; and knowing that this aged and unenlightened clergyman had had this living for forty-eight years, and having therefore reason to believe, that the gospel scarcely ever had been preached in that place; I had it in my heart to preach again in the afternoon. But I had no second sermon committed to memory. It came, however, to my mind to read the 5th chapter of Matthew, and to make such remarks as I was able. I did so. Immediately upon beginning to expound “Blessed are the poor in spirit, &c.” I felt myself greatly assisted; and whereas in the morning my sermon had not been simple enough for the people to understand it, I now was listened to with the greatest attention, and I think was also understood. My own peace and joy were great. I felt this a blessed work. After the service I left the aged clergyman as soon as possible, lest I should lose my enjoyment.
Source: George Müller, A Narrative of Some of the Lord’s Dealings with George Müller, vol. 1 (London: J. Nisbet & Co., 1860), 21–22.