Chapter 17 · verse 15 · gita.yoga.org

Bhagavad Gita 17.15

अनुद्वेगकरं वाक्यं सत्यं प्रियहितं च यत्।स्वाध्यायाभ्यसनं चैव वाङ्मयं तप उच्यते

Speech that causes no excitement, is truthful, pleasant, and beneficial; the practice of studying the Vedas is called austerity of speech.