Mercy is the most benevolent of the Knightly Virtues. Knights were duty bound to show mercy. Granted their duty extended only in showing mercy to the poor and oppressed, they were to be mericless to the evil-doers.
The paradigm of knightly etiquette and chivalry is that of the King Arthur's Knights of the Round Table. In some of the myths that surround this legendary company, the genesis of Knightly Mercy is explained. Sir Gawain, at Queen Guinevere's marriage feast, accidentally slays a maiden and refuses to grant mercy to another knight. As his penance he is required to always serve all maids and always grant mercy.
Mercy is defined as the disposition to be compassionate or forbearing. Even more so, a knight was expected to show mercy towards those that were their enemies. In the year 1346, the Siege of Calais began, and it cost many lives to both the English and the French. Finally, once the French King deseret the city to the English, the French citizens asked for mercy. The English Prince Edward demanded that six burgesses be delivered to him to be put to death as well as the keys to the city and towers, and the rest of Calais could go free. The six richest burgesses of Calais consented and were marched to their deaths before the Prince of England. Yet, at the begging of his wife, Edward showed mercy and allowed the six to be freed. This is one example of Knightly Mercy. Edward had been so upset at the length of the siege, yet he was still able to find compassion enough to set the city free.
Masons are expected to do the same. A mason is taught by the compasses the extent of his mercy, charity, faith, etc. Remember, the compasses teach us to circumscribe our desires and keep our passions within due bounds, towards all mankind, more especially a brother mason. I have read that "the distinguishing characteristic of a good Freemason are virtue, honour, and mercy, and may they ever by found in every Mason's heart." A Mason is obligated to show forth mercy, not only to his brethren, but also to those who are not.
When emotions become a little heated, a Mason should be able to step back and look at the situation reasonably. He should then be able to ere on the side of compassion. When someone comes before a Mason, full of ignorance and hate for who he his, he should be forbearing, being patient and having self control with annoyances and provocations. A Mason, just as the knights of old, should be full of mercy.