Srimad Bhagavatam Canto 05, Chapter 03, Text 20

SB 5.3.20

barhisi tasminn eva visnudatta bhagavan paramarsibhih prasadito nabheh priya-cikirsaya tad-avarodhayane merudevyam dharman darsayitu-kamo vata-rasananam sramananam rsinam urdhva-manthinam suklaya tanuvavatatara.
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
O Visnudatta, Pariksit Maharaja, the Supreme Personality of Godhead was pleased by the great sages at that sacrifice. Consequently the Lord decided to personally exhibit the method of executing religious principles [as observed by brahmacaris, sannyasis, vanaprasthas and grhasthas engaged in rituals] and also satisfy Maharaja Nabhi’s desire. Consequently He appeared as the son of Merudevi in His original spiritual form, which is above the modes of material nature.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
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-guna, rajo-guna and tamo-guna). Mayavadi philosophers say that the impersonal God appears in this material world by accepting a body in the sattva-guna. Srila Visvanatha Cakravarti states that the word sukla means “consisting of suddha-sattva.” Lord Visnu descends in His suddha-sattva form. Suddha-sattva refers to the sattva-guna which is never contaminated. In this material world, even the mode of goodness (sattva-guna) is contaminated by tinges of rajo-guna and tamo-guna. When sattva-guna is never contaminated by rajo-guna and tamo-guna, it is called suddha-sattva. Sattvam visuddham vasudeva-sabditam (Bhag. 4.3.23). That is the platform of vasudeva, whereby the Supreme Personality of Godhead, Vasudeva, can be experienced. In Bhagavad-gita (4.7) Sri Krsna Himself says:
yada yada hi dharmasya
 glanir bhavati bharata
abhyutthanam adharmasya
 tadatmanam srjamy 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 dharman darsayitu-kama — 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. Dharmam tu saksad bhagavat-pranitam. (Bhag. 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. Srimad-Bhagavatam refers to man-made dharma as kaitava-dharma, cheating religion. The Supreme Lord sends an avatara (incarnation) to teach human society the proper way to execute religious principles. Such religious principles are bhakti-marga. As the Supreme Lord Himself says in Bhagavad-gita: sarva-dharman parityajya mam ekam saranam vraja. The son of Maharaja Nabhi, Rsabhadeva, appeared on this earth to preach the principles of religion. That will be explained in the Fifth Chapter of this Fifth Canto.
Thus end the Bhaktivedanta purports of the Fifth Canto, Third Chapter, of the Srimad-Bhagavatam, entitled “Rsabhadeva’s Appearance in the Womb of Merudevi, the wife of King Nabhi.”
Srimad Bhagavatam Canto 05, Chapter 03, Text 19
Srimad Bhagavatam Canto 05, Chapter 03 Overview