Srivaishnavas, followers of Ramanuja, believe in the concept of prapatti or Saranagati, where, if I understand correctly, God himself becomes the savior after the devotee surrenders completely to God. People are welcome to correct me, if I misunderstood.
Now here is my question. Where is the concept of Prapatti mentioned in the mukhya upanishads, as per the Sri Vaishnava interpretation? Please cite commentaries or works of Sri Vaishnava acharyas to support your statements. The exact word "prapatti/saranagati" need not be there. It is sufficient if the concept is present. (Here, by mukhya upanishads, I mean the main upanishads (about 10-15) and not all the 108 upanishads).