Krishna descends as avatara out of compassion to reclaim fallen souls from material misery through devotional service.Listen — Srila Prabhupada Uvaca
Prabhupāda: ajo 'pi..., ajo 'pi sann avyayātmā bhūtānām īśvaro 'pi san prakṛtiṃ svām adhiṣṭhāya sambhavāmy ātma-māyayā [Bg 4.6] [Although I am unborn and My transcendental body never deteriorates, and although I am the Lord of all sentient beings, I still appear in every millennium in My original transcendental form.] Now, Lord Śrī Kṛṣṇa is describing how He incarnates Himself for the benefit of conditioned souls in the material world. The Supreme Personality of Godhead, He descends. The Sanskrit word is avatāra. Avatāra.
Avatāra, avatāram. Avatāra means who comes from higher plane down to this material world. He's called avatāra. So sometimes Lord Śrī Kṛṣṇa comes Himself, and sometimes He sends His representative also, for deliverance of the conditioned souls.
Now, now the principal religions of the world—Hindu religion, Muslim religion, Christian religion and Buddha religion—most of them believes some supreme authority or personality coming down from the kingdom of God. Just like in your Christian religion Lord Jesus Christ, he claimed to be the son of God and coming from the kingdom of God to reclaim you. So this claim of Lord Jesus Christ we admit. We, the followers of Bhagavad-gītā, we admit this claim.
So there is no difference of opinion between the followers of Hindu religion and Christian religion. In details there may be, according to country, climate and people, in details there may be difference, but that does not make any material difference. So far devotional service is concerned, now, there are several items for offering devotional service to the Lord. They are called, śravaṇaṃ kīrtanaṃ viṣṇoḥ smaraṇaṃ pāda-sevanam arcanaṃ vandanaṃ dāsyaṃ sakhyam ātma-nivedanam [SB 7.5.23] [There are six principles favorable to the execution of pure devotional service: (1) being enthusiastic, (2) endeavoring with confidence, (3) being patient, (4) acting according to regulative principles [such as śravaṇaṃ kīrtanaṃ viṣṇoḥ smaraṇam—hearing, chanting and remembering Kṛṣṇa], (5) abandoning the association of nondevotees, and (6) following in the footsteps of the previous ācāryas. These six principles undoubtedly assure the complete success of pure devotional service.] These are nine.
Now here, in this room, we are performing the process of śravaṇam and kīrtanam. Just like we chanted, Hare Kṛṣṇa Hare Kṛṣṇa Kṛṣṇa Kṛṣṇa Hare Hare Hare Rāma Hare Rāma Rāma Rāma Hare Hare [My dear Lord and the spiritual energy of the Lord, kindly engage me in Your service. I am now embarrassed with this material service. Please engage me in Your service.] This is reciprocation of śravaṇam and kīrtanam, hearing and chanting, that I chanted, you heard, and you chanted, I heard.
Reciprocation. So this is..., these two methods are the first method in devotional service. Śravaṇaṃ kīrtanam. And, and what about hearing and chanting? Now, Viṣṇu.
Viṣṇu means the Supreme Lord. Viṣṇu. Not any other thing. If we make chanting and hearing in some other subject matter, no, that will not do.