Paritrănăya Sădhunăm, Vinăshăyashcha Dushkrutăm
Dharma Sansthăpanăthăya Sambhavămi Yuge Yuge ll
Meaning:
To protect the good, destroy the wicked, establish Dharma or right conduct on earth, I shall be born from age to age.
(This was said by Lord Krishna while giving the Gita Updesh to Arjun during the war.)
Amongst the Trinity of Gods, that is , Brahmă, Vishnu and Mahesh; Vishnu who is known as the Preserver of the Universe , seeks from time to time to redeem the world and as an Avatăr (Incarnation) manifests his Divine Being into the life of man, whenever evil threatens it.
Buddhă Avatăr was added later . Some texts replace Balarăma to add Buddhă, believing that Balarăma was the incarnation of the sepent (Ananta) on which Vishnu reclined.