How do Sri Vaishnavas know that the Alwars were incarnations of Nitya Suris?
Nitya Suris are the eternally inhabitants of Vaikunta who have never entered samsara.
The Alwars were ancient Tamil saints who sang the Naalayira Divya Prabhandham, which are considered equivalent to the Vedas according to Sri Vaishnavas.
My question is, how do Sri Vaishnavas know that these saints were incarnations of Nitya Suris?
Now there is a scriptural prophecy for at least one of the Alwars, namely Nammalwar, which says that he will be an incarnation of Vishvaksena (a nitya suri), but what about the other Alwars? Are there scriptural prophecies for them?