Shiva Purana
अर्धमात्रात्मको नादः श्रूयते लिंगमूर्धनि ॥ विभक्ते ऽपि तदा तस्मिन्प्रणवे परमाक्षरे ॥ ५ ॥
A half-voiced sound is heard at the head of the penis. Even when it was divided into that supreme syllable oṁkāra.
english translation
ardhamAtrAtmako nAdaH zrUyate liMgamUrdhani ॥ vibhakte 'pi tadA tasminpraNave paramAkSare ॥ 5 ॥
hk transliteration by Sanscript