naham prakasah sarvasya
mudho ’yam nabhijanati
loko mam ajam avyayam
I am never manifest to the foolish and unintelligent. For them I am covered by My internal potency, and therefore they do not know that I am unborn and infallible.
Commentary by Srila Prabhupada
It may be argued that since Krishna was present on this earth and was visible to everyone, then why isn’t He manifest to everyone now? But actually He was not manifest to everyone. When Krishna was present there were only a few people who could understand Him to be the Supreme Personality of Godhead. In the assembly of Kurus, when Sisupala spoke against Krishna’s being elected president of the assembly, Bhishma supported Him and proclaimed Him to be the Supreme God. Similarly, the Pandavas and a few others knew that He was the Supreme, but not everyone. He was not revealed to the nondevotees and the common man. Therefore in the Bhagavad-gita Krishna says that but for His pure devotees, all men consider Him to be like themselves. He was manifest only to His devotees as the reservoir of all pleasure. But to others, to unintelligent nondevotees, He was covered by His internal potency.
In the prayers of Kunti in the Srimad-Bhagavatam (1.8.19) it is said that the Lord is covered by the curtain of yoga-maya and thus ordinary people cannot understand Him. This yoga-maya curtain is also confirmed in the Isopanishad (mantra 15), in which the devotee prays:
tat tvam pusann apavrnu
“O my Lord, You are the maintainer of the entire universe, and devotional service to You is the highest religious principle. Therefore, I pray that You will also maintain me. Your transcendental form is covered by the yoga-maya. The brahmajyoti is the covering of the internal potency. May You kindly remove this glowing effulgence that impedes my seeing Your sac-cid-ananda-vigraha [Bs. 5.1], Your eternal form of bliss and knowledge.” The Supreme Personality of Godhead in His transcendental form of bliss and knowledge is covered by the internal potency of the brahmajyoti, and the less intelligent impersonalists cannot see the Supreme on this account.
Also in the Srimad-Bhagavatam (10.14.7) there is this prayer by Brahma: “O Supreme Personality of Godhead, O Supersoul, O master of all mystery, who can calculate Your potency and pastimes in this world? You are always expanding Your internal potency, and therefore no one can understand You. Learned scientists and learned scholars can examine the atomic constitution of the material world or even the planets, but still they are unable to calculate Your energy and potency, although You are present before them.” The Supreme Personality of Godhead, Lord Krishna, is not only unborn but also avyaya, inexhaustible. His eternal form is bliss and knowledge, and His energies are all inexhaustible.
Commentary by Sri Visvanatha Cakravarti Thakur
“If you have eternal form, qualities and pastimes, then why do we not see these things at all times?”
I am not manifest to all people living at all times and places. I am always present with my associates, qualities and pastimes in some universe, at some time, but just as the sun is not visible to all people at all times, but only sometimes, being covered by Mount Meru, I also am sometimes not visible, being covered by yogamaya.”
“So you say that though the sun is situated within the zodiac and is always present there for all the living beings there, is not visible to a particular person at all times and places. It is visible at some times, in some places such as Bharata, to the people present there. You say that you are similar to that. But as the sun is always visible in its own abode, why is Krishna not always visible to all the people presently dwelling in his abodes like Mathura and Dvaraka?”
“If Meru were present in the middle of the effulgent zodiac, then the sun, being covered, would not be visible. In the same way, within Krishna’s effulgent abodes, yogamaya is always present like Meru. Krishna, like the sun, covered by that Meru in the form of yogamaya, is not visible constantly, but only sometimes. This is all without fault.
“And the foolish people do not understand me at all in my form as Syamasundara (mam), being unborn though appearing as Vasudeva’s son (ajam), and free from material birth (avyayam). Thus, finally rejecting me, the ocean of auspicious qualities, they worship my impersonal aspect, brahman.”