At the end of the story when the fallen angel Michael is explaining who he is, why he had been condemned to live as a human being, and what he had learned, he tells about the rich man who had ordered the pair of boots made from a piece of expensive German leather. The customer is arrogant and overbearing. He calls the cobbler a fool. Naturally the poor cobbler is intimidated and then horrified when he sees that the fallen angel has turned the leather into a pair of soft slippers instead of a pair of boots.
"A man came to order boots that should wear for a year without losing shape or cracking. I looked at him, and suddenly, behind his shoulder, I saw my comrade—the angel of death. None but me saw that angel; but I knew him, and knew that before the sun set he would take that rich man's soul. And I thought to myself, 'The man is making preparations for a year, and does not know that he will die before evening.' And I remembered God's second saying, 'Learn what is not given to man.'
"What dwells in man I already knew. Now I learnt what is not given him. It is not given to man to know his own needs. And I smiled for the second time. I was glad to have seen my comrade angel—glad also that God had revealed to me the second saying."
Michael does not say exactly what happened to the rich man except that he had died before sunset on the very same day that he had come to the cobbler's house to order the boots. No doubt he died of a heart attack or a stroke. What is important is that Michael learned the second lesson he had been sent to earth to learn. It is not given to man to know his own needs. Michael had disobeyed the rich man's orders and had used the expensive leather to make a pair of slippers instead of a pair of boots, but it turned out that they were exactly what were required, because the customer was going to be buried in them.
"What Men Live By" is an example of the kind of fiction Tolstoy wrote after his religious conversion in late middle age. He repudiated his own most famous works, War and Peace and Anna Karenina, because he had become thoroughly disillusioned by and alienated from the members of his own elite social class, who played the major roles in those novels. He only respected men and women who lived by their own labor, and he tried to emulate them. He learned to become a cobbler. He opened a school for peasant children, and tried, often against the opposition of his own wife, to live a simple, humble life, based on the teachings of Jesus Christ as recorded in the gospels rather than on the teachings of the Russian Orthodox Church, from which he had been ostracized for heresy.