SB 11.17.13
vipra-ksatriya-vit-sudra
mukha-bahuru-pada-jah
vairajat purusaj jata
ya atmacara-laksanah
Translation:
In Treta-yuga the four social orders were manifested from the universal form of the Personality of Godhead. The brahmanas appeared from the Lord’s face, the ksatriyas from the Lord’s arms, the vaisyas from the Lord’s thighs and the sudras from the legs of that mighty form. Each social division was recognized by its particular duties and behavior.