As a temple or a church is kept clean each day, the inner body, the temple of the soul, should be cleansed with a copious supply of blood through āsana and prānāyāma. They cleanse the body physically, physiologically and intellectually. The body, having its own intelligence, develops its potential to change its behavioral patterns. It helps the sādhaka to detach himself from sensual desires and guides him toward the holder of the body, the soul. Thus śauca (cleanliness) makes the body a fit instrument for the pursuit of spiritual knowledge.
— Yogācārya B.K.S. Iyengar, Light on Yoga Sūtras of Patañjāli, commentary on sūtra II.40. 

Day before the Intensive with Manouso Manos at the Abode of Iyengar Yoga:
Now the Patañjāli is oiled with charred coconut many times, many verses and sūtras chanted. Many hands clean, fold and arrange the many props for the many students.