The heathen armies may intend to capture the city, but verse 12 tells us that these nations do not know what is in the LORD’s mind. His intention is the exact opposite of theirs. They thought that they could destroy Jerusalem, but the Lord has actually brought them together in order to destroy them. What is in the LORD’s mind is Good News Translation‘s way of expressing what is more literally “the thoughts of the LORD” and “his plan” (Revised Standard Version). Translators may use either of these ideas, or both of them. One possible way of expressing the sense is “they do not know what the Lord is planning to do (to them).”
The destruction of the nations is described by a comparison with grain (“corn” in the British edition), which is brought in sheaves or bundles “to the threshing floor” (Revised Standard Version) to be threshed, that is, beaten in order to separate the ears, or heads, from the stalks. Just as grain is gathered together from the fields in order to be threshed, so the nations have been gathered together. This implies something that the Hebrew makes explicit, namely, that the Lord is the one who gathered them. In many languages it will be necessary to state clearly that the Lord is the actor. The reason that the Lord has brought these nations together is so that they can be punished. The punishment means that these nations will suffer the defeat they intended to inflict on Jerusalem.
A popular way of threshing in Old Testament times was to have cattle pull a threshing machine over the wheat. These machines had sharp stones or metal on the bottom, and this was an effective picture of how the nations were to be punished. This verse does not say just what method of threshing the prophet had in mind, though verse 13 does suggest that cattle were involved in some way. If a person is translating for a culture that has any kind of threshing, the ordinary term for it should be acceptable as long as the comparison of threshing to punishment will be understood by the readers. If threshing is not known, it may be possible to drop the comparison to threshing and to say simply “the Lord has gathered them together in order to punish them.” However, even in this case it may be possible to use a descriptive phrase to try to keep the comparison. One suggestion may be “just as farmers bring their wheat together in order to beat it and separate the part that is eaten.”
Quoted with permission from Clark, David J. et al. A Handbook on Micah. (UBS Helps for Translators). New York: UBS, 1978, 1982, 1993. For this and other handbooks for translators see here .