Mahabharata 13.58.32

13.58.32

atra te vartayiṣyāmi yathā dharmaḥ sanātanaḥ |
rājanyo brāhmaṇaṃ rājanpurā paricacāra ha |
vaiśyo rājanyamityeva śūdro vaiśyamiti śrutiḥ || 32 ||

As women have one eternal duty, in this world, viz., dependence upon and obedient service to their husbands, and as such duty constitutes their only end, even so is the service to Brahmanas Our eternal duty and end. If, at sight of cruelties and other sinful acts in Kshatriyas, the Brahmanas, O son, unhonoured by us, forsake us all, I say, of what use would life be to us, in the absence of all contact with the Brahmanas, especially as we shall then have to drag on our existence without being able to study the Vedas to perform sacrifices, to hope for worlds of bliss hereafter, and to achieve great feats? I shall, in this connection, tell thee what the eternal usage is. In days of yore, O king, the Kshatriyas used to serve the Brahmanas. The Vaisya in a similar manner used in those days to worship the royal order, and the Sudra to worship the Vaisya. Even this is what is heard. The Brahmana was like a blazing fire. Without being able to touch him or approach his presence, the Sudra used to serve the Brahmana from a distance. It was only the Kshatriya and the Vaisya who could serve the Brahmana by touching his person or approaching his presence. The Brahmanas are endued with a mild disposition. They are truthful in behaviour. They are followers of the true religion. When angry, they are like snakes of virulent poison. Such being their nature, do thou, O Yudhishthira, serve and attend upon them with obedience and reverence.