Śrī Īśopaniṣad advises us to pour water on the root, the source of all germination. Worship of the mass of humanity by rendering bodily service, which can never be perfect, is less important than service to the soul. The soul is the root that generates different types of bodies according to the law of karma. To serve human beings by medical aid, social help and educational facilities while at the same time cutting the throats of poor animals in slaughterhouses is no service at all to the soul, the living being.
The living being is perpetually suffering in different types of bodies from the material miseries of birth, old age, disease and death. The human form of life offers one a chance to get out of this entanglement simply by reestablishing the lost relationship between the living entity and the Supreme Lord. The Lord comes personally to teach this philosophy of surrender unto the Supreme, the sambhūta. Real service to humanity is rendered when one teaches surrender to and worship of the Supreme Lord with full love and energy. That is the instruction of Śrī Īśopaniṣad in this mantra.
The simple way to worship the Supreme Lord in this age of disturbance is to hear and chant about His great activities. The mental speculators, however, think that the activities of the Lord are imaginary; therefore they refrain from hearing of them and invent some word jugglery without any substance to divert the attention of the innocent masses of people. Instead of hearing of the activities of Lord Kṛṣṇa, such pseudo spiritual masters advertise themselves by inducing their followers to sing about them. In modern times the number of such pretenders has increased considerably, and it has become a problem for the pure devotees of the Lord to save the masses of people from the unholy propaganda of these pretenders and pseudo incarnations.
The Upaniṣads indirectly draw our attention to the primeval Lord, Śrī Kṛṣṇa, but the Bhagavad-gītā, which is the summary of all the Upaniṣads, directly points to Śrī Kṛṣṇa. Therefore one should hear about Kṛṣṇa as He is by hearing from the Bhagavad-gītā or Śrīmad-Bhāgavatam, and in this way one's mind will gradually be cleansed of all contaminated things. Śrīmad-Bhāgavatam (1.2.17) says, "By hearing of the activities of the Lord, the devotee draws the attention of the Lord. Thus the Lord, being situated in the heart of every living being, helps the devotee by giving him proper directions." The Bhagavad-gītā (10.10) confirms this: dadāmi buddhi-yogaṁ taṁ yena mām upayānti te.