While carrying the form of the Supreme Personality of Godhead within the core of his heart, Vasudeva bore the Lord’s transcendentally illuminating effulgence, and thus he became as bright as the sun. He was therefore very difficult to see or approach through sensory perception. Indeed, he was unapproachable and unperceivable even for such formidable men as Kaṁsa, and not only for Kaṁsa but for all living entities.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
स बिभ्रत्पौरुषं धाम भ्राजमानो यथा रविः । दुरासदोऽतिदुर्धर्षो भूतानां सम्बभूव ह
sa bibhratpauruṣaṃ dhāma bhrājamāno yathā raviḥ | durāsado'tidurdharṣo bhūtānāṃ sambabhūva ha
SB 10.2.17