अनुद्वेगकरं वाक्यं सत्यं प्रियहितं च यत्।स्वाध्यायाभ्यसनं चैव वाङ्मयं तप उच्यते।।17.15।।
anudvega-karaṁ vākyaṁ satyaṁ priya-hitaṁ cha yat svādhyāyābhyasanaṁ chaiva vāṅ-mayaṁ tapa uchyate
Speech that causes no excitement, is truthful, pleasant, and beneficial; the practice of studying the Vedas is called austerity of speech.