Srimad-Bhagavatam: Canto 9 - Chapter 1 - Verse 12
Sanskrit:
याच्यमाना: कृपणया राममात्रातिदारुणा: ।प्रसह्य शिर उत्कृत्य निन्युस्ते क्षत्रबन्धव: ॥ १२ ॥
ITRANS:
yācyamānāḥ kṛpaṇayārāma-mātrātidāruṇāḥprasahya śira utkṛtyaninyus te kṣatra-bandhavaḥ
Translation:
With pitiable prayers, Reṇukā, the mother of Paraśurāma and wife of Jamadagni, begged for the life of her husband. But the sons of Kārtavīryārjuna, being devoid of the qualities of kṣatriyas, were so cruel that despite her prayers they forcibly cut off his head and took it away.