etad vam darsitam rupam
nanyatha mad-bhavam jñanam
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
I have shown you this form of Visnu 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, Visnu, has indeed appeared.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Devaki did not need to be reminded that the Supreme Personality of Godhead, Lord Visnu, had appeared as her son; she already accepted this. Nonetheless, she was anxious, thinking that if her neighbors heard that Visnu had appeared as her son, none of them would believe it. Therefore she wanted Lord Visnu to transform Himself into a human child. On the other hand, the Supreme Lord was also anxious, thinking that if He appeared as an ordinary child, she would not believe that Lord Visnu had appeared. Such are the dealings between devotees and the Lord. The Lord deals with His devotees exactly like a human being, but this does not mean that the Lord is one of the human beings, for this is the conclusion of nondevotees (avajananti mam mudha manusim tanum asritam). Devotees know the Supreme Personality of Godhead under any circumstances. This is the difference between a devotee and a nondevotee. The Lord says, man-mana bhava mad-bhakto mad-yaji mam namaskuru: “Engage your mind always in thinking of Me, become My devotee, offer obeisances and worship Me.” A nondevotee cannot believe that simply by thinking of one person, one can achieve liberation from this material world and go back home, back to Godhead. But this is a fact. The Lord comes as a human being, and if one becomes attached to the Lord on the platform of loving service, one’s promotion to the transcendental world is assured.