SB 11.15.24
parsnyapidya gudam pranam
hrd-urah-kantha-murdhasu
aropya brahma-randhrena
brahma nitvotsrjet tanum
Translation:
The yogi who has achieved the mystic perfection called svacchanda-mrtyu blocks the anus with the heel of the foot and then lifts the soul from the heart to the chest, to the neck and finally to the head. Situated within the brahma-randhra, the yogi then gives up his material body and guides the spirit soul to the selected destination.
Purport:
This mystic opulence of svacchandu-mrtyu, or dying at will, was wonderfully exhibited by Bhismadeva at the end of the Battle of Kuruksetra. According to Srila Sridhara Svami, the term brahma, as used in this verse, is an example of upalaksana, or the use of a general term to indicate various concepts. Brahma here indicates the particular destination selected by the yogi, namely the spiritual sky, the impersonal brahmajyoti or any other destination that has attracted the yogi’s mind.