Inner purity is possible when one remains in constant touch with the Soul. Constant Soul-Consciousness is the real purity.

As one indulges in deeper self-search he will know somewhere he is going wrong, and it is for him to   overcome the entire obstacle on his own by knowing what is obstructing his realization.  The greatest hindrance is mixing religion, god, scriptures, and yogic theories and intellectual speculations and logical conclusions. Moreover, attachment to scriptures, personal god and religious code of conduct keeps one permanently in the grip of duality.

The Upanishads declare:- 

Katha Upanishad 1:2:23 The Soul cannot be realized through hearing scholarly explanation 

of the discourses, not even by the intellect.

Katha Upanishad 1:3:6 “Through the knowledge of the Soul, God, one is pure and clean constantly.” Neither by reading the book, nor by taking a bath at holy place has one become pure. Inner purity is possible when one remains in constant touch with the Soul. Constant Soul-Consciousness is the real purity.

Kena Upanishad 2:4 When it is known through every state of cognition, it is rightly known, for (by such knowledge) one attains life eternal. Through one's own self one gains power and through wisdom one gains immortality.

Kena Upanishad 2:5

If here one knows it, then there is truth, and if here one knows it not, there is a great loss. Hence, seeing the Real in all beings, wise men become immortal on departing from this world.

Mundaka Upanishad 1:2:8

“Remaining in the fold of ignorance and thinking “we are extremely wise and learned,” the fools with boastful nature ramble about like the blind led by the blind alone.”

Mundaka Upanishad 3:2:3

“The weak and timid cannot realize the Self. Self-Realization is not possible through intellect or hearing spiritual discourse. One who welcomes God in every activity, through a thorough controlled and disciplined life, to him also the Soul is revealed."

Mundaka Upanishad 3:2:3:-
 

The Soul cannot be realized by the weak and timid.

RIG VEDA: - The famous utterance of Upanishad that Brahman cannot be attained by duality is in RV (5.12.2). The idea that Brahman cannot be attained by mere action or effort is in RV (8.70.3) and (5.48.5); Brahman cannot be approached by thought (RV.1.170.1 or Kena U., 1.3). [RV=RIG VEDA].

As indicated in ISH Upanishads: - By worshiping gods and goddesses you will go after death to the world of gods and goddesses. But will that help you? The time you spend there is wasted, because if you were not there you could have spent that time moving forward towards Self-knowledge, which is your goal. In the world of gods and goddesses you cannot do that, and thus you go deeper and deeper into darkness.

It clearly indicates that:-If the human goal is to acquire Self-Knowledge then why one has to indulge in rituals and glorifying the conceptual gods, goddesses and gurus to go in to deeper darkness. Instead   spend that time moving forward towards Self-knowledge, which is one’s prime goal.