from the book Encylcopedia of Freemasonry & its Kindred Sciences
by Albert C. Mackey M. D.
Mercy - The point of a Knight Templar's sword is said to be characterized by the quality of "mercy unrestrained" which reminds us of the Shakespearian expression—"the quality of mercy is not strained."
In the days of chivalry, mercy to the conquered foe was an indispensable quality of a knight. An act of cruelty in battle was considered infamous, for what ever was contrary to the laws of generous warfare was also contrary to the laws of chivalry (see Magnimous)