Via the lotus-stem-thread of the mouth, relinquish breath - meaning:  make is Still; in this way - via the sushumna path, it becomes Still like this spontaneously.  This is the indication of "kumbhak" - meaning: vayu moves in Stillness via the sushumna; that is the state of kumbhak

"Sreshtha uttamanga [the greatest and principal part of the body] (mouth)* brahmin" - when there is samadhi; the abode of all happiness is "swarga" [heaven]; when one performs Kriya, one is a "brahmin"; from that Mouth - Lord (Purushottama)."

The "mahadyuti" [Great Splendor] Kutastha is the secret Dharma of all dharma; He planned the different works of mouth, arms, thighs, feet and knees; brahmin - from the mouth; kshatriya - from the arms; vaishya - from the thighs; and shudra - from the legs/feet.

Purushottama manifests from the Mouth; by His wish there is "havya" and "kavya" [both are types of oblations] = the Divine Form is "kavya"-- Kutastha; all these merge into Brahman - meaning samadhi.

A brahmin eats all edibles by the Mouth - meaning: nothing at all remains except Brahman; He is beyond space - meaning Brahman -- when samadhi happens, everything including Kutastha is merged; what can be asked for other than this?