Bhagavatapurana 2.5.37

2.5.37

puruṣasya mukhaṃ brahma kṣatram etasya bāhavaḥ /
ūrvorvaiśyo bhagavataḥ padbhyāṃ śūdro vyajāyata //

37. And the Brahmana race issued from the mouth of Purusha; the Kshatriya race from His arms; the Vaisya race from His thigh, and the Sudra race from His feet.