Atharvasira Upanishad

It is among the 31 Upanishads associated with the Atharvaveda. It is classified as a Shaiva Upanishad focused on god Rudra. The Upanishad is notable for asserting that all gods are Rudra, everyone and everything is Rudra, and Rudra is the principle found in all things, their highest goal, the innermost essence of all reality that is visible or invisible. Rudra is Atman and Brahman, and in the heart. Rudra's symbol is Om, states the text, he can be realized by abandoning anger and lust, and through silence alone. The text is known for its monism (Advaita).