SB 11.21.6

vedena nāma-rūpāṇi
 viṣamāṇi sameṣv api
dhātuṣūddhava kalpyanta
 eteṣāṁ svārtha-siddhaye
Synonyms: 
vedena — by Vedic literature; nāma — names; rūpāṇi — and forms; viṣamāṇi — different; sameṣu — which are equal; api — indeed; dhātuṣu — in (material bodies composed of) the five elements; uddhava — My dear Uddhava; kalpyante — are conceived of; eteṣām — of them, the living entities; sva-artha — of self-interest; siddhaye — for the achievement.
Translation: 
My dear Uddhava, although all material bodies are composed of the same five elements and are thus equal, the Vedic literatures conceive of different names and forms in relation to such bodies so that the living entities may achieve their goal of life.
Purport: 

The words nāma-rūpāṇi viṣamāṇi refer to the system of varṇāśrama-dharma, in which members of human society are designated according to four social and four occupational divisions. Those dedicated to intellectual or religious perfection are called brāhmaṇas, those dedicated to political perfection are called kṣatriyas, those dedicated to financial perfection are called vaiśyas, and those dedicated to eating, sleeping, sex and honest work are called śūdras. Such propensities arise from the three modes of material nature (goodness, passion and ignorance), because the pure soul is not materially intellectual, ambitious for power, enterprising or servile. Rather, the pure soul is always absorbed in loving devotion to the Supreme Lord. If the various propensities of a conditioned soul are not engaged in the varṇāśrama system, they will certainly be misused, and thus that person will fall down from the standard of human life. The Vedic system is designed by the Lord so that conditioned souls may pursue their individual achievements and at the same time advance toward the ultimate goal of life, Kṛṣṇa consciousness. Just as a doctor deals with a crazy man by speaking to him sympathetically in terms of his false conception of life, one who understands the Vedic literature engages the living entities according to their illusory identification with the elements of matter. Although all material bodies are composed of the same material elements and are thus qualitatively identical, as described here by the word sameṣu, the Vedic social system, varṇāśrama, is created to engage all human beings in Kṛṣṇa consciousness according to their various degrees of material identification. The absolute good is the Supreme Lord Himself, and that which approaches the Supreme Lord becomes similarly good. Because the sun is the source of heat within this world, an object that approaches the sun becomes hotter and hotter until it merges into fire. In the same manner, as we approach the transcendental nature of the Personality of Godhead, we automatically become surcharged with absolute goodness. Although this knowledge is the real basis of the Vedic literature, mundane piety is enjoined and sin is prohibited so that one can gradually come to the platform of material goodness, whereupon spiritual knowledge becomes visible.