True incarnations of God reveal themselves through extraordinary characteristics, never through self-proclamation.Listen — Srila Prabhupada Uvaca
Prabhupāda: avatāra nāhi kahe-'āmi avatāra' muni saba jāni' kare lakṣaṇa-vicāra [Cc Madhya 20.354] [An actual incarnation of God never says ’I am God’ or ’I am an incarnation of God.’ The great sage Vyāsadeva, knowing all, has already recorded the characteristics of the avatāras in the śāstras.] So Lord Caitanya says that incarnation, He never advertises Himself that He is avatāra. But experienced muni, those who are liberated souls, those who are expert in Vedic knowledge, they understand that this is avatāra, or incarnation, by the symptoms, as they are stated in the scriptures. In the scripture, the color, the activities, the time and the place and the parents—everything is described about the incarnation. So, so that just like everything has to be understood by the symptoms, that is the scientific advancement.
Just like a drug is tested in the laboratory and the drug, the symptoms and the taste, how it is, how the color changes, how it tastes in the tongue, everything is described there, so scientists proves, understands, the genuineness of a particular chemical by testing. Similarly, nobody should be accepted as incarnation. That is foolishness. Incarnation, they are stated in the scriptures.
Their symptoms, everything is there, and one should understand from that. The avatāra never advertise. And anyone who advertises himself that "I am incarnation," he should be at once rejected. He should be at once rejected. yasyāvatāra jñāyante śarīriṣv aśarīriṇaḥ tais tair atulyātiśayair vīryair dehiṣv asaìgataiḥ [Cc Madhya 20.355] [The Lord does not have a material body, yet He descends among human beings in His transcendental body as an incarnation. Therefore it is very difficult for us to understand who is an incarnation. Only by His extraordinary prowess and uncommon activities, which are impossible for embodied living entities, can one partially understand the incarnation of the Supreme Personality of Godhead.] The first thing is that avatāra, incarnation, He hasn't got this material body. The first symptom is. And still, the avatāra appears before us.
Because, so far our senses are concerned, we can see the material objects. We can see a stone. We can see, I mean to say, wood. We can see water.
We cannot see even air, the finer material things. We cannot see mind. We know that mind there is in every soul, every body. Every one of us has got mind, but we cannot see.
We cannot see the sky. So the..., in the material world also, there are so many finer things which we cannot see. And what to speak of spiritual? So that spiritual, Supreme Spirit, when He appears before us, seeable, so that we can see, so that is His mercy. That is His mercy.
Because we cannot see even the soul within ourself; we are seeing only the body. So what to speak of the Supreme Spirit? That is not possible. Yasyāvatāra jñāyante śarīriṣv aśarīriṇaḥ.