http://www.indiandacoit.com/archive/2013/04/22/about-casts-and-inequalities-in-india-the-big-picture.html
Laws of Manu
Circa 100 BC
From his mouth God
created the Brahman (priest),
from his arms the Kshatriya (ruler),
from his thighs the Vaishya (commoner),
and from his feet the Shudra (servant)
Chapter 1, Verse 51