SB 3.12.41

The nucleus of the four social orders-brahmacarya or student life, grhastha or household family life, vanaprastha or retired life for practicing penance, and sannyasa or renounced life for preaching the truth-is the four legs of religion. The vocational divisions are the brahmanas or the intelligent class, the ksatriyas or administrative class, the vaisyas or mercantile productive class, and the sūdras or general laborer class who have no specific qualifications. All were systematically planned and created by Brahma for the regular promotion of self-realization. Student life is meant for acquiring the best education; household family life is meant for gratifying the senses, provided it is performed with a charitable disposition of mind. Retirement from household life is meant for penance, for advancement of spiritual life, and renounced life is meant for preaching the Absolute Truth to the people in general. The combined actions of all members of society make the whole situation favorable for the upliftment of the mission of human life. The beginning of this social institution is based on education meant for purifying the animal propensities of the human being. The highest purificatory process is knowledge of the Supreme Personality of Godhead, the purest of the pure.