One verse

Srimad Bhagavatam 7.15.36

7.15.36

य: प्रव्रज्य गृहात्पूर्वं त्रिवर्गावपनात्पुन: । यदि सेवेत तान्भिक्षु: स वै वान्ताश्यपत्रप: ॥ ३६ ॥

yah pravrajya grhat purvam tri-vargavapanat punah yadi seveta tan bhiksuh sa vai vantasy apatrapah

yah
one who
pravrajya
being finished for good and leaving for the forest (being situated in transcendental bliss)
grhat
from home
purvam
at first
tri-varga
the three principles of religion, economic development and sense gratification
avapanat
from the field in which they are sown
punah
again
yadi
if
seveta
should accept
tan
materialistic activities
bhiksuh
a person who has accepted the sannyasa order
sah
that person
vai
indeed
vanta-asi
one who eats his own vomit
apatrapah
without shame

One who accepts the sannyasa order gives up the three principles of materialistic activities in which one indulges in the field of household life—namely religion, economic development and sense gratification. One who first accepts sannyasa but then returns to such materialistic activities is to be called a vantasi, or one who eats his own vomit. He is indeed a shameless person.