देवद्विजगुरुप्राज्ञपूजनं शौचमार्जवम्। ब्रह्मचर्यमहिंसा च शारीरं तप उच्यते ॥

deva-dwija-guru-prājña- pūjanaṁ śhaucham ārjavam brahmacharyam ahinsā cha śhārīraṁ tapa uchyate

Worship given to the Gods, to the twice-born, to the teachers and to the wise, purity, straightforwardness, continence and harmlessness, are called the austerity of the body.

In plain words: Self-discipline of the body means respecting God, holy people, teachers and wise people. It also means being clean, honest, sexually self-controlled and never hurting anyone.