anudvega-karaṁ vākyaṁ satyaṁ priya-hitaṁ cha yat
svādhyāyābhyasanaṁ chaiva vāṅ-mayaṁ tapa uchyate||15||

Meaning : Speech that is free from agitation, truthful, pleasing, and beneficial; and the practice of studying sacred texts these are called austerity of the speech.