Essence of ChAndogya Upanishad: The Universe: Part-7B
When man becomes powerful (gains great strength), he rises (gains spiritual power); as he rises, he serves (Karma Yoga). as he serves, he associates with wise (Discipleship), he sees, hears (Sravana), thinks (Manana), knows (Nididhyasana), acts (intense Tapas), and he realizes (Attains Self).