Bhagwad Gita - Post 54

Paritraanaaya saadhunaam 

Vinaashaaya cha dushkritaam;

Dharma samsthaapanaarthaaya 

Sambhavaami yuge yuge.

For the protection of the good, for the destruction of the wicked, and for the establishment of righteousness, I am born in every age.

For what purpose does Lord Krishna manifest Himself? 

Anticipating such a question Lord Krishna responds for the protection of the righteous and virtuous and for the annihilation of the sinful and evil. 

To uphold the tenants and precepts of righteousness that makes sanathana dharma or eternal righteousness invulnerable. For this reason the Supreme Lord incarnates from age to age on particular occasions.

And what is to be protected and who / what is to be destructed and how?

In this age, everyone is but a mixture of good and bad. Since everyone has a strong steak of wicked in him, if the Lord goes on destructing all the wicked, it would result in extinction of the entire mankind. 

Instead, Lord has chosen to wield the weapon of LOVE or PREMA, destroying the wickedness in people. Thus, no one dies but everyone stands a chance in this Sai Era, to be transformed.  

The foundation for this were already laid during the earlier avatar of Rama and Krishna but it is in the age of Sai Avatar that Love has become the sole weapon. 

Swami says, 

“In this Kali age, the wicked have to be reformed and reconstructed, through love and compassion. 

That is why, this Avatar has come unarmed. It has come with the message of Love”.

“I am Love, always Love. God is Love and wherever there is pure love and love only, that is God”.

Sam-sthapana-arthaya-ca infers to establishing one’s true nature. The Lord's divine nature assumes His divine form. 

Because prakriti or material nature is understood as svabhava the word "sam" has been used referring to that. 

The word "sva" also refers Lord’s essential "svarupa" or transcendental nature  as "svabhava" refers to the innate form or essence and creation is manifested by this essence being the impulse of His will.

And, on His role in the mission of “Dharma-Sam-Sthapana-arthaya”, Swami says,

“There is considerable change in human outlook that I have to bring about. 

No one can stop Me or deter Me from fulfilling these tasks for which I have come, namely, the establishment of the one unchanging truth. In this task, you have a part to play….

You must take a path by which you can see deep in My heart, and experience the divine aspects of mine……”.

Swami clearly conveys on Dharma, for the establishment of which He incarnates from age to age. He says,

“The true Dharma is to be immersed in Atmic bliss.  In daily practice, when acts are motivated by the basic principle of Atmic reality, every act gets stamped with the seal of Dharma. 

But when acts are motivated by convenience and selfish interest, the dharma becomes a pseudo dharma.”

Love.