Bhagavad Gita · Chapter 17: The Three Kinds of Faith

Bhagavad Gita 17.14

devadvijaguruprājñapūjanaṃ śaucamārjavam | brahmacaryamahiṃsā ca śārīraṃ tapa ucyate ||

Honouring the gods, the twice-born, teachers, and the wise; purity, honesty, continence, and non-violence: these are called austerity of the body.

Modern context

Austerity of the body is not starving or self-torture, as warned against earlier. It is honouring those worthy of honour, keeping clean, being straightforward, practising self-restraint and not causing harm. This redefines austerity in a healthy, practical way. Real discipline is shown in respectful, honest and gentle conduct, not in suffering.