Listen to the recitation of the 8th verse, 2nd chapter of the Hatha Yoga Pradipika:
प्राणं सूर्येण चाकृष्य पूरयेद् उदरं शनैः ।
विधिवत् कुम्भकं कृत्वा पुनश् चन्द्रेण रेचयेत् ॥८॥
For more information, including the sanskrit text in devanagari and roman script, please check out the Hatha Yoga Pradipika Page on Hatha Yoga Pradipika II 8. Recitation by Sukadev Bretz from Yoga Vidya Germany.