Story of Tirumular
Sundaranāthar (Sanskrit: सुंदरनाथ), a yogi from Madurai, traveled to Mount Kailāsa. He spent five years of his life there and was initiated by Lord Shiva himself.
Lord Shiva sent him to Tamilakam (present-day Tamil Nadu) to meet sage Agasthya, who lived in the Pothigai Hills. After meeting Agasthya, he went to Chidambaram to worship Lord Shiva at the famous Nataraja temple.
When he was about to return to Mount Kailāsa, near Sathanur village (near Aduthurai, Kumbakonam, in the Thanjavur District), he saw a herd of cows crying. As he approached, he discovered the cowherd lying dead from a snakebite, and sensed the deep distress of the cows. Moved by their suffering, the yogi resolved to restore the cowherd's life. The yogi left his physical body (sthoola sharira) inside a hollow tree trunk and entered the body of Mulan (the cowherd) with his causal body (sookshma sharira), thus re-invigorating the life force within the body of Mulan.
After leading the cows safely home, the yogi, still in Mulan's body, returned to the forest, hoping to re-enter his own body. To his surprise, it was nowhere to be found—local forest dwellers had discovered it and assumed that someone had died trapped within the tree.
The divine voice of Lord Shiva informed the yogi that it was his wish for him to continue teaching about yoga and liberation in Mulan's body. Obeying Lord Shiva’s command, Sundaranāthar remained in Mulan's body, spreading the teachings of Shaiva Siddhanta in simple language that resonated with common folk, a stark contrast to the refined literary Tamil he once spoke.
Sundaranāthar, now in his humble new avatar, was revered by the people as TiruMular—the Venerated Cowherd—whose wisdom, once spoken through the language of sages, now flowed through the simple words of a common man. Seated beneath the sacred shade of a peepal tree in the quiet village of Thiruvavaduthurai, TiruMular entered deep meditation, where divine inspiration blossomed within him, leading to the creation of three thousand timeless hymns of Tamil Shaiva Siddhanta, which were later compiled and named Tirumantiram.
Tirumantiram forms one part of the 12 volumes of Tamil Shaiva philosophy collectively called Tirumurai, a compendium of works by the 63 Nayanars (poet-saints). TiruMular is also listed as one of the 18 Siddhars, perfected yogis who lived in physical form.