The main mention of the Ram mantra Agni Beejis found in the Srirama Rahasyopanishad , where the name Rama is said to contain the seeds of fire, air, and moon. This is an extremely powerful mantra associated with the navel chakra (solar plexus chakra), chanted for mental peace and energy.
Main Mantra: In Shri Ram Rahasya Upanishad, Ram Mantra is mentioned with seeds like Gloum, Om, Hreem etc.
Agni Beej: 'Ram' itself is considered to be an Agni Beej.
Other references: In Tantra and Yoga texts also, the name Ram is considered to be the seed mantra of the fire element of the navel chakra.
This mantra is used to increase energy, digestion power and strength.
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The Rama Rahasya Upanishad is generally considered a "late" Upanishad, with estimates for its composition ranging between the 9th and 11th centuries CE, or potentially as late as the 17th century. It belongs to the Atharva Veda and is part of the 108 Upanishads listed in the Muktikā canon.
Dating: While some sources place it in the 9th-11th century CE, others suggest it is a modern-era text from the 17th century.
Content: The text is dedicated to the worship of Lord Rama, identifying him as the supreme reality (Brahman) and the manifestation of Satcitananda (truth, consciousness, bliss).
Structure: It is largely presented as a dialogue involving Hanuman and includes Tantric elements such as the Ram-beej mantra.
Significance: It serves as a key text for the Ramanandi sect and other Vaishnava traditions.
It is not one of the ancient (pre-7th century BCE) Upanishads but rather a later sectarian text focusing on Ram Bhakti.