Verse
कृषिगौरक्ष्यवाणिज्यं वैश्यकर्म स्वभावजम् ।परिचर्यात्मकं कर्म शूद्रस्यापि स्वभावजम् ॥
Agriculture, cattle-keeping, trade inclusive of the labour of the craftsman and the artisan are the natural work of the Vaishya. All work of the character of service falls within the natural function of the Shudra.
Gītā 18·44