The Taoteching #31
Weapons are not auspicious tools
some things are simply bad
thus the Taoist shuns them
in peace the ruler honors the left
in war he honors the right
weapons are not a ruler’s tools
he wields them when he has no choice
dispassion is the best
thus he does not beautify them
he who beautifies them
enjoys killing others
he who enjoys killing others
achieves no worldly rule
thus we honor the left for joy
we honor the right for sorrow
the left is where the adjutant stands
the commander on the right
which means as at a funeral
when you kill another
honor him with your tears
when the battle is won
treat it as a wake
Lao-tzu
from The Taoteching