One verse

Srimad Bhagavatam 5.26.11

5.26.11

ये त्विह यथैवामुना विहिंसिता जन्तव: परत्र यमयातनामुपगतं त एव रुरवो भूत्वा तथा तमेव विहिंसन्ति तस्माद्रौरवमित्याहू रुरुरिति सर्पादतिक्रूरसत्त्वस्यापदेश: ॥ ११ ॥

ye tv iha yathaivamuna vihimsita jantavah paratra yama-yatanam upagatam ta eva ruravo bhutva tatha tam eva vihimsanti tasmad rauravam ity ahu rurur iti sarpad ati-krura-sattvasyapadesah.

ye
those who
tu
but
iha
in this life
yatha
as much as
eva
certainly
amuna
by him
vihimsitah
who were hurt
jantavah
the living entities
paratra
in the next life
yama-yatanam upagatam
being subjected to miserable conditions by Yamaraja
te
those living entities
eva
indeed
ruravah
rurus (a kind of envious animal)
bhutva
becoming
tatha
that much
tam
him
eva
certainly
vihimsanti
they hurt
tasmat
because of this
rauravam
Raurava
iti
thus
ahuh
learned scholars say
ruruh
the animal known as ruru
iti
thus
sarpat
than the snake
ati-krura
much more cruel and envious
sattvasya
of the entity
apadesah
the name

In this life, an envious person commits violent acts against many living entities. Therefore after his death, when he is taken to hell by Yamaraja, those living entities who were hurt by him appear as animals called rurus to inflict very severe pain upon him. Learned scholars call this hell Raurava. Not generally seen in this world, the ruru is more envious than a snake.