Albert Barnes Commentary Jeremiah 36:23

"And it came to pass, when Jehudi had read three or four leaves, that [the king] cut it with the penknife, and cast it into the fire that was in the brazier, until all the roll was consumed in the fire that was in the brazier." — Jeremiah 36:23 (ASV)

Leaves - Columns: literally folding-doors; the word exactly describes the shape of the columns of writing on the scroll.

Penknife - “ Scribe’s knife;” used to shape the reed for writing, and to make erasures in the parchment.

On the hearth - Or, in the fire-pan. The conduct of the king shows how violent was his temper.