Sage Sankara says:~ Of what avail are the Vedas and (other) Scriptures, Mantras (sacred formulae) and medicines to such a one?+

Lord Krishna himself says that he can do nothing to make a man intelligent straight away. The adepts give Prasad, blessing, initiations, mantras, etc. only to confer temporary peace of mind, to help you to get rid of worries, but not to confer Gnana. The capacity to receive it must first be inborn in man by evolutionary degree. 

The mantra-yoga consists of repeating the name of God, or even the AUM; thousands of times yield nothing. It can appeal only to the ignorant, to those who cannot think deeper. It is merely a  religious fable. The real exercise is to think of the meaning of the name or the AUM and then only do you get something.

Mantras can do nothing. If they really had any power why did not Krishna use one to stop the Mahabharata war? All the magical power of mantras are religious fables because religion is based on the false Self (waking or ego) and false experience(waking or world)  Visions and Samadhi are illusions from the standpoint of the Soul the  Self. 

No mantras help to get rid of ignorance. All the mantras and rituals are meant for the ignorant populace, which strongly believes, the world in which he exists as a reality.  For one who wants to acquire self-knowledge or Brahma Gnana or Atma Gnana, the mantas will not help to realize the truth, which is beyond form, time, and space.

That is why Sage Sankara VC~.61. For one who has been bitten by the serpent of Ignorance, the only remedy is the knowledge of Brahman. Of what avail are the Vedas and (other) Scriptures, Mantras (sacred formulae), and medicines to such a one?

VC-  v6~ Let erudite scholars quote all the scripture, let Gods be invoked through sacrifices, let elaborate rituals be performed, let personal gods be propitiated---yet, without the realization of one‘s identity with the Self, there shall be no liberation for the individual, not  even in the lifetimes of a hundred Brahmas put together

Sage Sankara goes on to say: ~A sickness of not cured by saying the word “medicine.” You must take the medicine. Liberation does not come by merely saying the word “Brahman.” Brahman must be experienced. Until you allow this apparent universe to dissolve from your consciousness until you have realized Brahman, how can you find liberation just by saying the word Brahman? The result is merely noise. Until a man has destroyed his enemies and taken possession of the splendor and wealth of the kingdom, he cannot become a king by simply saying “I am a king.”

A buried treasure is not uncovered by merely uttering the words: “Come forth.” You must follow the right directions, dig, remove the stones and earth from above it, and then make it your own. In the same way, the pure truth of the Atman, which is buried under Maya and the effects of Maya, can be reached by meditation, contemplation, and other spiritual disciplines but never by subtle arguments. : ~ Santthosh Kumaar