Charles Spurgeon Commentary Isaiah 41:15

"Behold, I have made thee [to be] a new sharp threshing instrument having teeth; thou shalt thresh the mountains, and beat them small, and shalt make the hills as chaff." — Isaiah 41:15 (ASV)

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.

You know the threshing sledge was made rough at the bottom, as though it had sharp teeth, and when it was drawn over the wheat after it was spread out on the threshing-floor, the grain was separated from the chaff. So God tells his people, if they trust him, that he will make them into a threshing instrument having teeth, and they will thresh, not ordinary harvests, but thresh the mountains, and beat them small, and make the hills as chaff. No task is too hard for God's people to accomplish when God is with them; difficulties vanish, and their fears are driven before the wind, when God strengthens them.

Behold, I will make you a new sharp threshing instrument having teeth:

He will make poor feeble worms to be like that great threshing sledge which they were accustomed to draw over the straw to bruise out the wheat.

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.

People in the East drag a wooden machine over the corn to extract 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.