Vijnana Bhairava Tantra
न व्रजेन्न विशेच्छक्तिर्मरुद्रूपा विकासिते । I निर्विकल्पतया मध्ये तया भैरवरूपता ॥ २६ ॥
When Shakti in the form of vayu or pranic air is still and does not move swiftly in a specific direction, there develops in the middle, through the state of Nirvikalpa, the form of Bhairava.
english translation
na vrajenna vizecchaktirmarudrUpA vikAsite । I nirvikalpatayA madhye tayA bhairavarUpatA ॥ 26 ॥
hk transliteration by Sanscript