Shiva Purana
न मुंचति न गृह्णाति वायुमंतर्बहिः स्थितम् ॥ संपूर्णं कुंभवत्तिष्ठेदचलः स तु कुंभक ॥ २४ ॥
He does not breathe out the internal or breathe in the external air. He remains steady like the fìlled-up jar. It is called Kumbhaka (Retention).
english translation
na muMcati na gRhNAti vAyumaMtarbahiH sthitam ॥ saMpUrNaM kuMbhavattiSThedacalaH sa tu kuMbhaka ॥ 24 ॥
hk transliteration by Sanscript