What is yoga?

“When his mind, intellect and self are under control, freed from restless desire, so that they rest in the spirit within, a man becomes a Yukta – one in communion with God. A land does not flicker in a place where no winds blow; so it is with a yogi, who controls his mind, intellect and self, being absorbed in the spirit within him. When the restlessness of the mind, intellect and self is stilled through the practice of Yoga, the yogi by the grace of the spirit within himself finds fulfillment. Then he knows the joy eternal which is beyond the pale of the senses which his reason cannot grasp. He abides in this reality and move not therefrom. He has found the treasure above all others. There is nothing higher than this. He who has achieved it, shall not be moved by the greatest sorrow. This is the real meaning of Yoga – a deliverance from contact with pain and sorrow.”

-Sri Krishna

Excerpt from –
“Light on Yoga by: B.K.S. Iyengar