Ivan the simple peasant shows himself to be more powerful than the forces of evil. Whereas his brothers are either greedy or militaristic, he just gets on with tending to his plot of land, working away each day without any fuss.
This makes it comically impossible for the Devil and his minion, a little imp sent by the Prince of Darkness to cause trouble for Ivan, to make life hard for him. No matter how hard they try, they are never able to disrupt Ivan's life, and their increasingly desperate attempts provide much of the story's humor.
The imp tries to put all kinds of obstacles in Ivan's way. He floods his hayfield with water, which leaves the grass covered with mud. But instead of throwing his hands up in despair, Ivan simply resolves to do all the mowing, even if it will take him all week.
Upon hearing this, the imp realizes he is dealing with a tough customer, so he tries a different dodge. This time, he hides in the grass and grabs Ivan's scythe by the heel in an attempt to stop him from mowing the grass. But Ivan's not to be deterred and swings the scythe with all his might, cutting off half the imp's tale in the process.
The now-dock-tailed imp tries again, hoping to get the better of Ivan when he comes to harvest the oats. But by the time he wakes up the following morning, he's shocked to discover that the oats have already been mown. Ivan has defeated him again.
A subsequent attempt to rot Ivan's stock of rye is also a failure, as is the imp's offer to make soldiers out of anything. That's because Ivan has, for Tolstoy at least, the right values. He simply cannot be tempted by the Devil and his minion.