Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 45
Sanskrit:
एषा तवानुजा बाला कृपणा पुत्रिकोपमा । हन्तुं नार्हसि कल्याणीमिमां त्वं दीनवत्सल: ॥ ४५ ॥
ITRANS:
eṣā tavānujā bālākṛpaṇā putrikopamāhantuṁ nārhasi kalyāṇīmimāṁ tvaṁ dīna-vatsalaḥ
Translation:
As your younger sister, this poor girl Devakī is like your own daughter and deserves to be affectionately maintained. You are merciful, and therefore you should not kill her. Indeed, she deserves your affection.