SB 11.17.15
varnanam asramanam ca
janma-bhumy-anusarinih
asan prakrtayo nrnam
nicair nicottamottamah
Translation:
The various occupational and social divisions of human society appeared according to inferior and superior natures manifest in the situation of the individual’s birth.
Purport:
According to Srila Visvanatha Cakravarti Thakura, the brahmanas and sannyasis, being situated on the head of the universal form of the Lord, are considered to be the most
qualified, whereas the sudras and grhasthas, being on the legs or loins of the Personality of Godhead, are considered to be in the lowest position. A living entity is born with a certain amount of intelligence, beauty and social opportunity, and he is therefore situated in a particular occupational and social position within the varnasrama system. Ultimately, such positions are external designations, but since the majority of human beings are conditioned by the external energy of the Lord, they should act according to the scientific varnasrama divisions until they reach the stage of jivan-mukta, or liberated life.