O King, that personality whom, out of ignorance only, you thought to be your maternal cousin, your very dear friend, well-wisher, counselor, messenger, benefactor, etc., is that very Personality of Godhead Śrī Kṛṣṇa.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
यं मन्यसे मातुलेयं प्रियं मित्रं सुहृत्तमम् । अकरोः सचिवं दूतं सौहृदादथ सारथिम्
yaṃ manyase mātuleyaṃ priyaṃ mitraṃ suhṛttamam | akaroḥ sacivaṃ dūtaṃ sauhṛdādatha sārathim
SB 1.9.20