The Greatest Commentary
Eeḍu ('the Match / The Equal' — because it matches the Tiruvāymozhi in depth and richness) is the popular name for the Mupatthāṟṟāyirappaḍi vyākhyānam — the thirty-six thousand paḍi (verses/units) commentary on Nammāzhvār's Tiruvāymozhi. It records the oral exposition of Nampiḷḷai and was written down by his disciple Vaṭakku Tiruvīdhippiḷḷai. Thus Nampiḷḷai is the source of the teaching, while Vaṭakku Tiruvīdhippiḷḷai is the redactor of the received written commentary.
How It Was Preserved
Nampiḷḷai expounded the Tiruvāymozhi in his kālakṣepam sessions, and his disciple Vatakku Tiruvīdhip Piḷḷai secretly recorded the full exposition. When Nampiḷḷai discovered this, rather than being displeased, he had the manuscript completed and blessed — the hidden recording became the authorized text.
Scale and Significance
The Eeḍu is the central text of Teṅkalai learning. A complete kālakṣepam of the Eeḍu — expounding all 36,000 paḍis — takes months to complete. Its rich anecdotes about prior Ācāryas, its vivid doctrinal interpretations, and its warm devotional tone make it indispensable for understanding the Tiruvāymozhi.