Sri Ramanuja Acharyas Guru initiated him into Narayana Mahamantra. He told him not to pass it on to any body. Sri Ramanuja asked his Guru what is the fruit of Chanting of Narayana Mahamantra. His Guru told him that one who chants Narayana Mahamantra will go to Vaikunta, abode of the Lord. If somebody tells the mantra to people who are not initiated, he will go to hell.
Sri Ramanuja out of pure compassion, ran to the hillock in the village and started chanting the Mantra and invited all people to join. He didnot mind going to hell while those who listen going to Vaikunta. Such was his compassion.