In verses 15-16 God makes extensive use of farming imagery, especially that of harvesting grain. He uses this imagery to describe how Israel will defeat its enemies.

As in verse 11, the word Behold calls attention to what God will do for Israel right after he told them not to be afraid (see the comments there).

I will make of you a threshing sledge, new, sharp, and having teeth: For threshing sledge, see the comments on 28.27. Here it is a metaphor for Israel. Just as a farmer uses a threshing sledge to separate the good grain from the useless stalks and chaff, so God will use Israel to punish its enemies. The sledge is described as new, sharp, and having teeth, which means it is very effective. The adjective new may describe the sledge (so Bible en français courant) or the metal pieces (teeth) underneath it (so Good News Translation, Die Bibel im heutigen Deutsch). The adjective sharp clearly describes its metal pieces. Having teeth is literally “master of mouths.” New Jerusalem Bible has “double teeth” and New American Bible says “double-edged” since the Hebrew word for “mouths” is a double form of the word for “mouth” (see Psa 149.6, where Revised Standard Version renders this word “two-edged”). In this context it is better to say “many teeth” or simply “teeth.”

For cultures where the threshing sledge is unknown, it would be helpful to include an illustration of one here or at 28.27. Translators should also consider including a footnote describing it more fully since a long expression for it would destroy the poetic balance of the lines.

You shall thresh the mountains and crush them, and you shall make the hills like chaff: In these parallel lines mountains and hills are used figuratively, but what these two words represent has been a challenge for interpreters. Some have suggested that they refer to Israel’s enemies, and that the “threshing” points to Israel’s punishment of them. Others think that they are figures for Israel’s present difficulties that it will overcome. We prefer the first view, but since the specific reference is not clear, translators should retain the metaphors. Israel will thresh (see the comments on 21.10) and crush the mountains just as a sledge threshes and crushes stalks of grain. The Hebrew verb rendered crush can refer to grinding something so fine that it is nothing but dust, so New Jerusalem Bible translates the third line as “you will thresh and beat the mountains to dust” (similarly New Jewish Publication Society’s Tanakh). This rendering forms a suitable parallel to the next line.

And you shall make the hills like chaff indicates what the hills will become. Chaff is the outside skin of kernels of grain that comes off the grain in the threshing process (see the comments on 17.13). The wind can easily blow it away (see verse 16). Here it is an image of something useless, to be discarded or thrown away. New Jerusalem Bible and Bible en français courant have “straw.” Languages that do not have a word for chaff may say “dried grass” or “dead leaves.”

Translation examples for this verse are:

• Look, I will make you like a new threshing sledge with sharp teeth;
you will thresh the mountains and crush them to dust,
and make the hills like chaff.

• See, I will make you like a threshing sledge,
to which are attached sharp new nails;
you will thresh the mountains and turn them to dust,
and the hills you will turn into chaff.

Quoted with permission from Ogden, Graham S. and Sterk, Jan. A Handbook on Isaiah. (UBS Helps for Translators). New York: UBS, 2011. For this and other handbooks for translators see here .