It is not as important to slay your enemy outside the city as it is not to let him into the city.
Do not cast out a demon with a demon. For you will always have a demon in the house. But cast out the devil with God. And the devil will flee, but God will remain.
Do not fight fire with fire. For you will make the fire into a conflagration, and your house will burn down along with your enemy’s. But fight fire with water and you will extinguish it.
Do not raise death as a weapon against death, for you will only increase the range of death. But raise life as a weapon against death, and death will retreat as a shadow does before the face of the sun.
St. Nicolai Velemirovich, Prayers by the Lake, Prayer LXII.