Srimad-Bhagavatam: Canto 9 - Chapter 1 - Verse 3


पृषध्रस्तु मनो: पुत्रो गोपालो गुरुणा कृत: ।पालयामास गा यत्तो रात्र्यां वीरासनव्रत: ॥ ३ ॥


pṛṣadhras tu manoḥ putrogo-pālo guruṇā kṛtaḥpālayām āsa gā yattorātryāṁ vīrāsana-vrataḥ


Among these sons, Pṛṣadhra, following the order of his spiritual master, was engaged as a protector of cows. He would stand all night with a sword to give the cows protection.


One who becomes vīrāsana takes the vow to stand all night with a sword to give protection to the cows. Because Pṛṣadhra was engaged in this way, it is to be understood that he had no dynasty. We can further understand from this vow accepted by Pṛṣadhra how essential it is to protect the cows. Some son of a kṣatriya would take this vow to protect the cows from ferocious animals, even at night. What then is to be said of sending cows to slaughterhouses? This is the most sinful activity in human society.