Bhagavad Gita: Chapter 17, Verse 15

अनुद्वेगकरं वाक्यं सत्यं प्रियहितं च यत् |
स्वाध्यायाभ्यसनं चैव वाङ्मयं तप उच्यते || 15||

anudvega-karaṁ vākyaṁ satyaṁ priya-hitaṁ cha yat
svādhyāyābhyasanaṁ chaiva vāṅ-mayaṁ tapa uchyate

anudvega-karamnot causing distress; vākyamwords; satyamtruthful; priya- hitambeneficial; chaand; yatwhich; svādhyāya-abhyasanamrecitation of the Vedic scriptures; cha evaas well as; vāṅ-mayamof speech; tapaḥausterity; uchyateare declared as

Translation

BG 17.15: Words that do not cause distress, are truthful, inoffensive, and beneficial, as well as the regular recitation of the Vedic scriptures—these are declared as the austerity of speech.

Commentary

Austerity of speech is speaking words that are truthful, unoffending, pleasing, and beneficial for the listener. The practice of the recitation of Vedic mantras is also included in the austerities of speech. The progenitor, Manu, wrote:

satyaṁ brūyāt priyaṁ brūyān na brūyāt satyam apriyam

priyaṁ cha nānṛitaṁ brūyāt eṣha dharmaḥ sanātanaḥ (Manu Smṛiti 4.138)[v4]

“Speak the truth in such a way that it is pleasing to others. Do not speak the truth in a manner injurious to others. Never speak untruth, though it may be pleasant. This is the eternal path of morality and dharma.”