Bhagawad Ramanujar had mentioned about the greatness of Bharnayasam extensively in Gitabashyam and Gadhyatrayam.
Notes:
Followers of Thenkalai sompradayam do not render Sharanagati based on the principle that Bhagavan protects out of his causeless mercy. Sharanagati is a part of austerities for Vadakalai followers.