देवद्विजगुरुप्राज्ञपूजनं शौचमार्जवम् ।ब्रह्मचर्यमहिंसा च शारीरं तप उच्यते ॥
devadvijaguruprājñapūjanaṃ śaucamārjavam |brahmacaryamahiṃsā ca śārīraṃ tapa ucyate ||
Reverence for the gods, the twice-born, teachers and the wise; purity, uprightness, celibacy and non-violence — this is called the austerity of the body.
Explanation
Krishna is describing three kinds of austerity (tapas), the disciplined effort that refines a person, beginning with the body. It consists in honoring the gods, the twice-born (dvija, those initiated into Vedic study, usually taken as Brahmins), teachers and the wise, together with cleanliness (śauca), straightforwardness (ārjava), chastity (brahmacarya) and non-harming (ahiṁsā). Commentators differ on whether brahmacarya here means strict celibacy or sexual restraint suited to one's stage of life.