Therefore, the doubts that have arisen in your heart out of ignorance should be slashed by the weapon of knowledge. Armed with yoga, O Bhārata, stand and fight.

Bhagavad Gita 4.42.

This sword of knowledge comes from two sources,  it is a double bladed sword.

One side is from association of saints

The other side is the association of saints via their literature.

Thus, Sadhu sanga Sastra sanga , in Vedic terms.

What is the fight ?

The Christian says fight the good fight with all thy might , but without weapons, how can you fight ? You will be killed immediately on the battlefield .

The field of material activities is also described in the Bhagavad Gita, God is the knower of all fields , and to understand the field and the knower of the field one requires knowledge, without which one will be ploughed over and buried in the material energies suffering repeatedly death ,thus, you’ll be defeated and your war will be lost .

So Krishna says, “Take up your weapons of knowledge and slay the demon of ignorance ” that keeps us  repeatedly taking birth and suffering all kinds of misery , although thinking  we might  find permanent happiness.

The permanency of consciousness is spoken of in theological cultures as well as the permanency of energies beyond Atoms elements and compounds , thus, the full plethora of energies are realised by one who has knowledge .

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