הִנֵּ֣ה שַׂמְתִּ֗יךְ לְמוֹרַג֙ חָר֣וּץ חָדָ֔שׁ בַּ֖עַל פִּֽיפִיּ֑וֹת תָּד֤וּשׁ הָרִים֙ וְתָדֹ֔ק וּגְבָע֖וֹת כַּמֹּ֥ץ תָּשִֽׂים׃
看哪，我使你成為新的、帶有利齒的打穀板，滿是鋒刃；你必踹踏眾山，將它們壓得粉碎，又使岡陵如同糠秕。
Rashi
a...grooved threshing sledge It is a heavy wooden implement made with many grooves, similar to the ironsmiths’ tool known as ‘lime’ in French, a file, and they drag it over the straw of the ears of grain and it cuts them until they become fine straw.
Ibn Ezra
למורג A threshing instrument. It is well known.22A.V., "Sharp." Comp. המוריגים threshing instruments (2 Sam. 24:22).
Rashi
new When it is new, before the points of its grooves are smoothed off, it cuts very much, but when it becomes old, the points of the grooves are smoothed off.