The seer is really the Self, the pure one, the ever holy, the infinite, the immortal. That is the Self of man.

Verse 2.5

अनित्याअशुचिदुःखानात्मसु नित्यशुचिसुखाअत्मख्यातिरविद्या ॥५॥

anityā-aśuci-duḥkha-anātmasu nitya-śuci-sukha-ātmakhyātir-avidyā ॥5॥

Mistaking the transient for the permanent, the impure for the pure, pain for pleasure, and that which is not the self for the self: all this is called lack of spiritual knowledge, avidya.

Verse 2.6

दृग्दर्शनशक्त्योरेकात्मतैवास्मिता ॥६॥

dr̥g-darśana-śaktyor-ekātmata-iva-asmitā ॥6॥

Egoism is the identification of the seer with the instrumental power of seeing.

All these various sorts of impression have one source: ignorance. We have first to learn what ignorance is. All of us think that “I am the body,” and not the Self, the pure, the effulgent, the ever blissful, and that is ignorance. 

We think of Unreal as Real, Real as Unreal and this is ignorance.

The seer is really the Self, the pure one, the ever holy, the infinite, the immortal. 

That is the Self of man. 

And what are the instruments? The Chitta, or mind-stuff, the Buddhi, intellect, the Manas, or mind, and the Indriyas, or sense organs.

These are the instruments for him to see the external world, and the identification of the Self with the instruments is what is called the ignorance.

We say “I am the mind, I am thought; I am angry, or I am happy.”

How can we be angry, and how can we hate? Because of identifying with our body thus see Duality.

We should identify ourselves with the Self; that cannot change.

 If it is unchangeable, how can it be one moment happy, and one moment unhappy?

It is formless, infinite, omnipresent. What can change it? Beyond all law. 

What can affect it? Nothing in to the universe can produce an effect on it, yet, through ignorance, we identify ourselves with the mind-stuff, and think we feel pleasure or pain.

PATANJALI YOGA SUTRAS