When the Supreme Lord appears or descends as an incarnation within this material world, He does not accept a body made of the three modes of material nature (sattva-guṇa, rajo-guṇa and tamo-guṇa). Māyāvādī philosophers say that the impersonal God appears in this material world by accepting a body in the sattva-guṇa. Śrīla Viśvanātha Cakravartī states that the word śukla means "consisting of śuddha-sattva." Lord Viṣṇu descends in His śuddha-sattva form. Śuddha-sattva refers to the sattva-guṇa which is never contaminated. In this material world, even the mode of goodness (sattva-guṇa) is contaminated by tinges of rajo-guṇa and tamo-guṇa. When sattva-guṇa is never contaminated by rajo-guṇa and tamo-guṇa, it is called śuddha-sattva. Sattvaṁ viśuddhaṁ vasudeva-śabditam (SB 4.3.23). That is the platform of vasudeva, whereby the Supreme Personality of Godhead, Vāsudeva, can be experienced. In Bhagavad-gītā (BG 4.7) Śrī Kṛṣṇa Himself says:
- yadā yadā hi dharmasya
- glānir bhavati bhārata
- abhyutthānam adharmasya
- tadātmānaṁ sṛjāmy aham
"Whenever and wherever there is a decline in religious practice, O descendant of Bharata, and a predominant rise of irreligion—at that time I descend Myself."
Unlike ordinary living entities, the Supreme Lord is not forced by the modes of material nature to appear. He appears dharmān darśayitu-kāma—to show how to execute the functions of a human being. The word dharma is meant for human beings and is never used in connection with beings inferior to human beings, such as animals. Unfortunately, without being guided by the Supreme Lord, human beings sometimes manufacture a process of dharma by concoction. Actually dharma cannot be made by man. Dharmaṁ tu sākṣād bhagavat-praṇītam. (SB 6.3.19) Dharma is given by the Supreme Personality of Godhead, just as the law is given by the state government. Man-made dharma has no meaning. Śrīmad-Bhāgavatam refers to man-made dharma as kaitava-dharma, cheating religion. The Supreme Lord sends an avatāra (incarnation) to teach human society the proper way to execute religious principles. Such religious principles are bhakti-mārga. As the Supreme Lord Himself says in Bhagavad-gītā: sarva-dharmān parityajya mām ekaṁ śaraṇaṁ vraja (BG 18.66). The son of Mahārāja Nābhi, Ṛṣabhadeva, appeared on this earth to preach the principles of religion. That will be explained in the Fifth Chapter of this Fifth Canto.