One verse

Srimad Bhagavatam 9.2.9

9.2.9

तं शशाप कुलाचार्य: कृतागसमकामत: । न क्षत्रबन्धु: शूद्रस्त्वं कर्मणा भवितामुना ॥ ९ ॥

tam sasapa kulacaryah krtagasam akamatah na ksatra-bandhuh sudras tvam karmana bhavitamuna

tam
him (Prsadhra)
sasapa
cursed
kula-acaryah
the family priest, Vasistha
krta-agasam
because of committing the great sin of killing a cow
akamatah
although he did not want to do it
na
not
ksatra-bandhuh
the family member of a ksatriya
sudrah tvam
you have behaved like a sudra
karmana
therefore by your fruitive reaction
bhavita
you shall become a sudra
amuna
because of killing the cow.

Although Prsadhra had committed the sin unknowingly, his family priest, Vasistha, cursed him, saying, "In your next life you shall not be able to become a ksatriya. Instead, you shall take birth as a sudra because of killing the cow."