Jeremiah 36:23 And it came to pass, that when Jehudi had read three or four leaves, he cut it with the penknife, and cast it into the fire that was on the hearth, until all the roll was consumed in the fire that was on the hearth.

Jeremiah 36:23 And it came about, when Jehudi had read three or four columns, [the king] cut it with a scribe's knife and threw [it] into the fire that was in the brazier, until all the scroll was consumed in the fire that was in the brazier.

23. three or four leaves--not distinct leaves as in a book, but the consecutive spaces on the long roll in the shape of doors (whence the Hebrew name is derived), into which the writing is divided: as the books of Moses in the synagogue in the present day are written in a long parchment rolled round a stick, the writing divided into columns, like pages.
pen-knife--the writer's knife with which the reed, used as a pen, was mended. "He" refers to the king (Jer 36:22). As often as Jehudi read three or four columns, the king cut asunder the part of the roll read; and so he treated the whole, until all the parts read consecutively were cut and burnt; Jer 36:24, "all these words," implies that the whole volume was read through, not merely the first three or four columns (1Ki 22:8).

JFB.

Jeremiah 36 Images and Notes

Brief Summary: Here is another expedient tried to work upon this heedless and untoward people, but it is tried in vain. A roll of a book is provided, containing an abstract or abridgment of all the sermons that Jeremiah had preached to them, that they might be put in mind of what they had heard and might the better understand it, when they had it all before them at one view. Now here we have, I. The writing of this roll by Baruch, as Jeremiah dictated it (v. 1-4). II. The reading of the roll by Baruch to all the people publicly on a fast-day (v. 5-10), afterwards by Baruch to the princes privately (v. 11-19), and lastly by Jehudi to the king (v. 20, v. 21). III. The burning of the roll by the king, with orders to prosecute Jeremiah and Baruch (v. 22-26). IV. The writing of another roll, with large additions, particularly of Jehoiakim's doom for burning the former (v. 27-32).

Outline
Baruch is to write the prophecies of Jeremiah. (1-8)
The princes advise them to hide themselves. (9-19)
The king having heard a part, burns the roll. (20-32)

Painted sketch of ancient writing instruments