Four often-cited verses (14-18) from the Advayataraka Upanishad reverentially narrate a Guru or teacher. The best Acharya (आचार्य, spiritual teacher), state verses 14-15, is one knows the Vedas, a devotee of the god Vishnu, has no spite, who knows yoga, has his own views on it, Yoga is part of how he lives his life, is clean, reveres his own Guru, and who understands the concept of Purusha (Atman-Brahman).