Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 65: Viśvāmitra Becomes a Brahmarṣi
Text 1.65.7

तथैवासीत्पुनर्मौनमनुच्छ्वासं चकार ह।
अथ वर्षसहस्रं वै नोच्छ्वसन्मुनिपुङ्गवः॥

tathaivāsīt punar maunam anucchvāsaṁ cakāra ha
atha
varṣa-sahasraṁ vai nocchvasan muni-puṅgavaḥ

tathā eva asīt punaḥ = again he took to; maunam = the vow of silence; anucchvāsam cakāra ha = and withheld his exhalation; atha varṣa-sahasram vai = for a thousand years; na ucchvasan = did not exhale; muni-puṅgavaḥ = that best of sages.

Again, he took to the vow of silence and withheld his exhalation. For a thousand years, that best of sages did not exhale.