Lord Śrī Kṛṣṇa said: O Arjuna, you should not show mercy by releasing this relative of a brāhmaṇa [brahma-bandhu], for he has killed innocent boys in their sleep.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
मैनं पार्थार्हसि त्रातुं ब्रह्मबन्धुमिमं जहि । योऽसावनागसः सुप्तानवधीन्निशि बालकान्
mainaṃ pārthārhasi trātuṃ brahmabandhumimaṃ jahi | yo'sāvanāgasaḥ suptānavadhīnniśi bālakān
SB 1.7.35