There is a way to live that will guarantee that we will be greeted with good from others. There is also a way of living and interacting with others that may give us an advantage in the short term, but in the long term will do us tremendous harm. The difference between these two lifestyles is found in how they treat others - especially when someone has done something wrong to them.
Our proverb begins by introducing us to someone called "the merciful man." This is the man who is gracious to others when they wrong him. He is called the "merciful man" because he delights in showing mercy to others. Mercy is best described this way. Not getting what we deserve. That may not sound all that great until you realize that the context for mercy is when you do something wrong, or act in a way that merits punishment. The man who shows mercy to others is willing to endure beging wronged. He does not always demand "fair" treatment when it comes to himself. He does not demand his pound of flesh whenever he is wronged. By doing this the Bible says that he does himself good. The literal Hebew here reads, "he does good to his own soul."
There are actually two benefits to being a "mercy-man." The first benefit is that others who receive mercy from you are far more likely to show you mercy as well. Jesus, in the Beattitudes, said this same thing. "Blessed are the merciful, for they shall receive mercy." When we show mercy, others are more apt to show us mercy as well. The second benefit is one we receive inwardly. The passage says that we do our souls' good. When we react with anger to every supposed slight and wrong, our spirit and our emotions are in a constant turmoil. That is not healthy for us - because stress levels will be elevated all the time. But when we learn to show mercy (and not take ourselves so seriously in the process) it will do wonders for our stress level.
The end of today's proverb deals with the problems that the "cruel man" brings upon himself. We read that the cruel man does himself harm. The Hebrew word for "cruel" here means someone who is fierce and who lacks any kind of sensitivity, compassion, or mercy towards others. Since we have an example from our news, I will use it to illustrate this. Ghadaffi was the leader of the nation of Libya. He was a living example of a "cruel man." He ruled with an iron fist over his people. He was not known for his wonderful acts of mercy, but rather for his horrible acts of cruelty. The day came when he no longer had an army to protect him. The media informed us of his last moments on this earth. He hid in a drainage pipe, hoping to escape those who were hunting him down. When they found him they treated him just as he had treated others. I won't go into detail as to what was done to him, but it was a horrible end. His cruelty was the example that was set for the people of his country. No wonder when he was caught he was subjected to the same lack of compassion and kindness he was known to use upon others.
The way we respond to others will prepare the way for our own treatment in life. That is why the man who chooses to show mercy will have good come upon him for his choice. The cruel man has a much different end. Having chosen a lack of compassion throughout his lifetime of interaction with others, he has nothing except the overflow of his own cruelty awaiting him in this life - and the full measure of God's wrath in the next.