अनुद्वेगकरं वाक्यं सत्यं प्रियहितं च यत् । स्वाध्यायाभ्यसनं चैव वाङ्मयं तप उच्यते ॥१५॥
anudvega-karaḿ vākyaḿ satyaḿ priya-hitaḿ ca yat svādhyāyābhyasanaḿ caiva vāń-mayaḿ tapa ucyate
anudvega-karam — not agitating; vākyam — words; satyam — truthful; priya — dear; hitam — beneficial; ca — also; yat — which; svādhyāya — of Vedic study; abhyasanam — practice; ca — also; eva — certainly; vāk-mayam — of the voice; tapaḥ — austerity; ucyate — is said to be.
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.
One should not speak in such a way as to agitate the minds of others. Of course, when a teacher speaks, he can speak the truth for the instruction of his students, but such a teacher should not speak to those who are not his students if he will agitate their minds. This is penance as far as talking is concerned. Besides that, one should not talk nonsense. The process of speaking in spiritual circles is to say something upheld by the scriptures. One should at once quote from scriptural authority to back up what he is saying. At the same time, such talk should be very pleasurable to the ear. By such discussions, one may derive the highest benefit and elevate human society. There is a limitless stock of Vedic literature, and one should study this. This is called penance of speech.