So Ṛṣabhadeva says: "My dear boys, you should not spoil this body, human form of body, like the hogs." He has specifically mentioned the name of the hogs, viḍ-bhujām. Then what it is meant for? He said, tapo divyam (SB 5.5.1). This human form of life is meant for austerity, penance. You should voluntarily accept some regulative principles, even they are not very much liking to you. Just like our students: they are, from the very beginning of their life, they are accustomed to certain habits, but we are restricting. We say, "You cannot do this," and they are accepting, following. This is called tapasya. Tapo. Tapasya.
Tapasya means I am habituated to smoking, suppose, and the spiritual master says: "You cannot smoke." So if he gives up smoking, he feels some inconvenience, some uncomfortable position. But because a spiritual master has ordered, he gives it up. This is called tapasya. Even at his inconvenience, he abides by the order of the spiritual master, regulative principle. That is called tapasya. He feels some inconvenience, but what can be done? He has accepted one spiritual master.
A spiritual master means voluntarily accepting a great personality whose rules and regulation he must abide by. This is accepting of spiritual master, voluntarily accepting somebody, "Yes, sir. Whatever you'll say, I'll accept." Śiṣya. Śiṣya means who abides by the rules. That is called śiṣya. Or English, "discipline." From discipline, disciplic, disciplic succession. From the discipline. So either you take English or Sanskrit, the same meaning. Śiṣya means who accepts the ruling of his spiritual master; and disciple means also the same thing: who becomes disciplined by the spiritual master.
So tapasya means even at the inconvenience of my personal comforts, I must abide by the orders of my spiritual master. This is called tapasya. And who is spiritual master? He does not manufacture any rules and regulation. He refers to the śāstra. Therefore Narottama dāsa Ṭhākura says, sādhu-śāstra-guru-vākya, tinete kariyā aikya. If you want to know who is a spiritual master, if you know who is a saintly person, then you should keep in the middle the śāstra, the scriptures, and you will corroborate.