Agnim-ile purohitam
Yajnasya devam ritvijam
Hotaram ratnadhatamam
(Rig Veda)

“All praise to Agni, inner purifying fire
(vehicle of sanctifying energy of light and warmth:
faith, enthusiasm, attention, spiritual yearning and commitment)
vibrant and pulsating within the body-mind complex!
Divine Radiance of the sanctifying enlightening energy having emerged
from the deeper cosmic order of existence!
Showering precious enlightening radiance on those
in whom and through whom It is ignited and properly nourished!

Agne naya supatha, raye asman
Visvani deva, vayunani vidvan
Yuyodhy asmaj juhuranam eno
Bhuyistham te nama uktim vidhema.
(Rig Veda)

“O Agni, Enlightening Purifying Energy,
elevate us to the right path, full of grace and joy!
Illuminator of everyone,
all our intents and deeds are never hidden from Your Light!
Burn away from us all our self-degrading contaminations
caused by the darkness of ignorance and delusion*!
To Thou, do we continuously offer our warmest salutation and reverence!”
********

यथैधांसि समिद्धोऽग्निर्भस्मसात्कुरुतेऽर्जुन ।
ज्ञानाग्निः सर्वकर्माणि भस्मसात्कुरुते तथा ॥

yathai’dhānsi samiddho’gnir bhasmasāt kurute’rjuna,
jānangniḥ sarvakarmāṇi bhasmasāt kurute tathā
(Bhagavad Gita – 4.37)

“As blazing fire turns fuel to ashes,
so verily O Arjun,
the fire of knowledge reduces all action to ashes.’’

Here we have a portrayal,
not of an introduction to knowledge through which one approaches yagya,
but of the culmination of knowledge or perception of God,
in which there is first the destruction of all unrighteous inclinations
and
in which then even the act of meditation is dissolved.

The one who had to be attained to has been attained.
Now who is there to look for by further meditation?
The sage with the wisdom that arises from perception of God brings his actions to an end.

But where does this perception of God occur?
Is it an external or internal phenomenon?

न हि ज्ञानेन सदृशं पवित्रमिह विद्यते ।
तत्स्वयं योगसंसिद्धः कालेनात्मनि विन्दति ॥

na hi jñānena sadṛśam pavitram iha vidyate,
tat svayam yogasamsiddhaḥ kālenā’tmani vindati
(Bhagavad Gita – 4.38)

“Doubtlessly nothing in the world is more purifying than this knowledge
and
your heart will realize it spontaneously
when you have attained to perfection on the Way of Action.”

Nothing in this world purifies as this knowledge does.
And this knowledge will be manifest to the doer alone,
not to anyone else, when his practice of yog has reached maturity,
not at its inception,
not in the middle,
not externally but within his heart-within his Self.

What is the required ability for this knowledge?

श्रद्धावाँल्लभते ज्ञानं तत्परः संयतेन्द्रियः ।
ज्ञानं लब्ध्वा परां शान्तिमचिरेणाधिगच्छति ॥

śraddhāvānl labhate jñānam tatparaḥ sanyatendriyaḥ,
jñānam labdhvā parām śāntim acireṇā’dhigacchati.
(Bhagwad Geeta – 4.39)

‘‘The worshipper of true faith who has subdued his senses
attains to this knowledge
and
at the very moment of attainment
he is rewarded with the benediction of supreme peace.”

For realization of God one needs to possess
faith, determination, and restraint of the senses.
If there is no intensely felt curiosity for the knowledge of God,
even taking refuge in a seer will not bring it.

Also, mere faith is not enough. 
The worshipper’s effort may be feeble .

Therefore, the determination to proceed resolutely along the prescribed way is a necessity.
Along with this it is also necessary to restrain the senses.

Realization of the Supreme God will not come easily to one who is not free from desire.

So only a man who has faith, enthusiasm for action,
and
restraint of the senses can have this knowledge.

And the very moment this knowledge dawns upon him,
he is blessed with the ultimate peace,
because after this there is left nothing more to strive for.
After this he will never know anything other than peace.