Srimad-Bhagavatam: Canto 7 - Chapter 1 - Verse 19

Sanskrit:

शपतोरसकृद्विष्णुं यद्ब्रह्म परमव्ययम् ।श्वित्रो न जातो जिह्वायां नान्धं विविशतुस्तम: ॥ १९ ॥

ITRANS:

śapator asakṛd viṣṇuṁyad brahma param avyayamśvitro na jāto jihvāyāṁnāndhaṁ viviśatus tamaḥ

Translation:

Although these two men — Śiśupāla and Dantavakra — repeatedly blasphemed the Supreme Personality of Godhead, Lord Viṣṇu [Kṛṣṇa], the Supreme Brahman, they were quite healthy. Indeed, their tongues were not attacked by white leprosy, nor did they enter the darkest region of hellish life. We are certainly most surprised by this.

Purport:

Kṛṣṇa is described by Arjuna in Bhagavad-gītā (10.12) as follows: paraṁ brahma paraṁ dhāma pavitraṁ paramaṁ bhavān. “You are the Supreme Brahman, the supreme abode and purifier.” Herein this is confirmed. Viṣṇuṁ yad brahma param avyayam. The Supreme Viṣṇu is Kṛṣṇa. Kṛṣṇa is the cause of Viṣṇu, not vice versa. Similarly, Brahman is not the cause of Kṛṣṇa; Kṛṣṇa is the cause of Brahman. Therefore Kṛṣṇa is the Parabrahman (yad brahma param avyayam).