I have shown you this form of Viṣṇu just to remind you of My previous births. Otherwise, if I appeared like an ordinary human child, you would not believe that the Supreme Personality of Godhead, Viṣṇu, has indeed appeared.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
एतद्वां दर्शितं रूपं प्राग्जन्मस्मरणाय मे । नान्यथा मद्भवं ज्ञानं मर्त्यलिङ्गेन जायते
etadvāṃ darśitaṃ rūpaṃ prāgjanmasmaraṇāya me | nānyathā madbhavaṃ jñānaṃ martyaliṅgena jāyate
SB 10.3.44