The materialist thinks that persons engaged in Krishna consciousness are crazy fellows wasting time by chanting Hare Krishna, but actually he does not know that he himself is in the darkest region of craziness because of accepting his body as permanent. And, in relation to his body, he accepts his home, his country, his society, and all other paraphernalia as permanent. This materialistic acceptance of the permanency of home, land, etc., is called the illusion of maya.
His Divine Grace A. C. Bhaktivedanta Swami Prabhupada
Srimad-Bhagavatam 3.30.3, Purport

Real heroism is to conquer one’s natural tendency to enjoy material life, and reality is seeing the Supreme Personality of Godhead everywhere.
Lord Sri Krishna
Srimad-Bhagavatam 11.19.37

By all methods of spiritual discipline, seeing the Lord in person is the true reward to be attained. That alone destroys illusion down to the root, so that pure love of God may flourish.
The Vaikuntha-dutas
Sri Brihad-bhagavatamrita 2.3.180

One who loudly chants the holy names of the Lord is a hundred times greater than one who silently chants, because those who chant silently purify only themselves, while those who chant loudly purify themselves as well as those who hear them.
Sri Prahlada Maharaja
Sri Naradiya Purana

Only the most fortunate can hear these four nectarean sounds – Krishna’s words, the tinkling of His ankle bells and bangles, His voice, and the vibration of His flute. If one does not hear these sounds, his ears are as useless as small conchshells with holes.
Sri Chaitanya Mahaprabhu
Sri Chaitanya-charitamrita, Antya-lila 17.48

The Vedas consist of nonmaterial sound, and they alone should be our pramana [evidence], because from them have issued all departments of knowledge, mundane and spiritual, among all schools of human thought since time immemorial.
Srila Jiva Goswami
Sri Tattva-sandarbha, Text 10

Though the water of the Ganges is pure and sweet, when received by the roots of bitter or poisonous trees growing on its bank it becomes distasteful sap. Similarly, when the Vedas come from the mouths of faithless people, the meaning becomes distasteful and gives results opposite to the normal results.
Srila Vishvanatha Chakravarti Thakura
Commentary on Srimad-Bhagavatam 11.14.8

One who always sees all living entities as spiritual sparks, in quality one with the Lord, becomes a true knower of things. What, then, can be illusion or anxiety for him?
Sri Ishopanishad, Mantra 7