Isha Upanishad (Īśā Upaniṣad) with commentaries of the famous Hindu Advaita Swāmī Shankara-Āchārya: The (Vedic) mantras (verses) beginning with Īśāvāsyam have not been utilised in karma (rituals etc.), for they serve to reveal the true nature of the Self, which is not an appendage to karma. The real nature of the Ātman consists in Its purity, sinlessness, oneness, eternity, incorporeity, omnipresence, etc.