Bhagavad Gita Chapter 18 Verse 44
कृृषिगौरक्ष्यवाणिज्यम्, वैश्यकर्म, स्वभावजम्,
परिचर्यात्मकम्, कर्म, शूद्रस्य, अपि, स्वभावजम्।।44।।
Krshigaurakshyavaanijyam’, vaishyakarm, swabhaavjam’,
Paricharyaatmkam’, karm, shoodrasya, api, swabhaavjam’ ||44||
Translation: (Krshigaurakshyavaanijyam’) for farming, protection of cows and for supporting oneself do trade of attainment of God (vaishyakarm, swabhaavjam’) are natural actions of a Vaishya and (paricharyaatkarm) to serve all the varnas and to do bhakti of the Supreme God are (shoodrasya) of Shudra (api) also (swabhaavjam’) natural (karm) actions. (44)
Translation: For farming, protection of cows and for supporting oneself do trade of attainment of God, these are natural actions of a Vaishya, and to serve all the varnas (castes) and to do bhakti of the Supreme God are also natural actions of a Shudra.