One verse

Srimad Bhagavatam 6.11.4

6.11.4

किं व उच्चरितैर्मातुर्धावद्भ‍ि: पृष्ठतो हतै: । न हि भीतवध: श्लाघ्यो न स्वर्ग्य: शूरमानिनाम् ॥ ४ ॥

kim va uccaritair matur dhavadbhih prsthato hataih na hi bhita-vadhah slaghyo na svargyah sura-maninam

kim
what is the benefit
vah
for you
uccaritaih
with those like the stool
matuh
of the mother
dhavadbhih
running away
prsthatah
from the back
hataih
killed
na
not
hi
certainly
bhita-vadhah
the killing of a person who is afraid
slaghyah
glorious
na
nor
svargyah
leading to the heavenly planes
sura-maninam
of persons who consider themselves heroes.

O demigods, these demoniac soldiers have taken birth uselessly. Indeed, they have come from the bodies of their mothers exactly like stool. What is the benefit of killing such enemies from behind while they are running in fear? One who considers himself a hero should not kill an enemy who is afraid of losing his life. Such killing is never glorious, nor can it promote one to the heavenly planes.