Isaiah 41:15

Isaiah 41:15. Behold, I will make thee a new sharp threshing instrument having teeth: thou shalt thresh the mountains, and beat them small. and shalt make the hills as chaff.

The Easterns drag a wooden machine over the corn to fetch out the grain from the ear. This is called a corn-drag, and they put teeth in it, similar to the teeth of a harrow. God said that he would turn his Church, his people, into a new corn-drag, with teeth sharp and tearing, and that they should go against their difficulties, which were like mountains, and against their trials, which were like hills, and they should thresh them small, and make them to be like chaff.