The faith goes as, though the Lord had delivered the knowledge of Ayurveda (oldest form of medicine know in India) to humans, people could still fell ill. Rightly it was a knowledge of cure illnesses of physical in nature. And, sometimes it is not just physical illness, but mental and emotional illness. Anger, lust, greed, jealousy etc… The result was increasing distress and diminishing wellbeing. With the objective of maintaining a lasting wellbeing all the sages gathered and once again restored to the Lord.
They narrated the whole ordeal to him and pleaded for knowledge, the science of keeping lasting wellbeing. To which the Lord agreed to grant the science of lasting wellbeing, in all his humbleness and love for beings.
Adi Shesha(the serpent with a 1000 heads, Lord’s closest associate and also his couch) who was already eager to take this knowledge, agreed to be born as human on behest of the Lord. Upon his birth he absorbed the knowledge from his mother who was an ascetic (a yogini and tapasvini), Gonika to latter disseminate it to people at large. And so, the world got its first every Yoga guru. The journey from cure to lasting wellbeing began with him giving the world ‘Yoga Sutra’