The Karma doctrine was originated with Upanishads (Gnostic texts) around 1600 BC. There are 200 plus scriptures in the Upanishads. The scriptures narrated well about transcendental self and its co-relation with ultimate reality. The Upanishads rest on the scriptures of Vedas and the teachings of the Upanishads created pre-classical Yoga era. (Rishi (sage) Vyasa compartmentalized Vedic hymns into four Vedic texts. They are Rig Veda (knowledge of praise), Yajur Veda (knowledge of sacrifice), Sama Veda (knowledge of chants) and Atharva Veda (knowledge of Atharvan). This was in around 1400 BC.
Bhagwad Gita written in around 500 BC owned prominent position in propagating Yoga. Bhagwad Gita is attributed to conversation between Prince Arjuna and the Godman Krishna. Bhagwat Gita gave importance in blending Jnana Yoga, Bhakti Yoga and Karma Yoga.