SB 8.5.41
vipro mukhad brahma ca yasya guhyam
rajanya asid bhujayor balam ca
urvor vid ojo ’nghrir aveda-sudrau
prasidatam nah sa maha-vibhutih
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The brahmanas and Vedic knowledge come from the mouth of the Supreme Personality of Godhead, the ksatriyas and bodily strength come from His arms, the vaisyas and their expert knowledge in productivity and wealth come from His thighs, and the sudras, who are outside of Vedic knowledge, come from His feet. May that Supreme Personality of Godhead, who is full in prowess, be pleased with us.