THE YOGA SUTRAS OF PATANJALI
Over 20 centuries ago, Patanjali assembled the oral knowledge of yoga into 196 aphorisms. These cover all aspects of life, beginning with a prescribed code of conduct and ending with one's vision of one's true self.
Sutra Study Resources
Sutra podcasts at RIMYI: http://yogasutras-rimyi.blogspot.com/
Light on the Yoga Sutras of Patanjali, B.K.S. Iyengar
Core of the Yoga Sutras, B.K.S. Iyengar
Study of Patanjali Yoga Sutras, Prashant Iyengar