Śivasaṃhitā 5.184

The economy of speech is as real a yoga as prāṇāyāma. Each unnecessary word expends prāṇa through the throat channel. The yogi who speaks only «words of highest good» is not taciturn from timidity but from understanding that valuable speech is concentrated like a laser: it penetrates where ordinary chatter only grazes the surface.

Sādhu-saṃlāpa is noble or virtuous conversation (sādhu = good, correct, saṃlāpa = conversation), the instruction to «not speak too much» (na bahuvacanam) is universal in yoga texts. Saṅga is attachment or company (saṅgha = group), tyāga renunciation, gṛha-karma domestic works.

This verse belongs to instructions on the yama-niyama of the gṛhastha (householder) yogi: one who lives in the world with family. Total isolation is not possible for them, but inner discipline within ordinary context is. Speech control (vāk-saṃyama) functions as a gateway to total discipline: when the tongue is controlled, the mind follows.