Srikantha Shivacharya in his commentary on Brahma Sutra 4.1.15 quotes various scripture showing the efficiacy of names of Lord Shiva. A relevant portion of that Bhasya is as:
But the Agnihotra and others (contribute) only to this effect thereof, as seen (in the scriptures.) (4.1.15).
The study of the Veda means the repeated japa or recitation of the Vedic mantras which treat of matters concerning Atman, which are calculated to produce the highest knowledge constituting the means of attaining the supreme Lord, Paramesvara. The Jabala- Upanishad says:
"Then the students of Brahman thus addressed him : Tell us, 0 Lord, what mantra has to be recited whereby to attain immortality ?" Yajnavalkya said : " It is by Satarudriya. These are indeed the names of the Immortal, and thereby one becomes immortal."
In the Kaivalya-Upanishad it is said:
"That Brahmana who daily recites Satarudriya, he is purified by the sacred fires; he is purified by the air, he, is purified from liquor-drinking, he is purified from Brahmanicide. Taking his stand in the final order of holy life, let a man recite it always or, once; he attains the highest knowledge; the Ocean of Samsara undergoes extinction."
Here we are given to understand that by the recitation of the mantras called Satarudriya which treat of Brahman, that supreme knowledge which extinguishes Brahman is attained, and that the sins which are opposed to the knowledge undergo destruction. The recitation of Satarudriya is here said to bring about destruction of all sins, on the ground that it comprises the names of Shiva who is immortal and free, through time without a beginning—as declared in the words " these indeed are the names of the immortal." From this it will be seen that even the recitation of the names of the Paramesvara such as 'Shiva,' —conduces to the destruction of all sins that may stand in the way of knowledge. The Sruti says:
"If even a Chandala, if he should utter the word 'Shiva', one may talk with him, dwell with him, eat with him."
Here indeed we are given to understand that the greatest sinner who is most impure attains highest purity by a mere utterance of the word 'Shiva' denoting Brahman. Elsewhere also the sruti, after saying that in the case of the Brahmana who recite daily the Atharvasiras all sins are extinguished declares also that he attains moksha, in the following words:
"Once reciting, he becomes clean, pure, and fit for sacrificial ritual. Reciting a second time, he attains the state of Ganapati; reciting it a third time he enters the Deva Himself."
And that the recitation of the Pranava. caases the break of the bond is taught in passages like the following:
"Having made Atman the arani, and Pranava the upper arani, by practice of knowledge, by repeated churning, the wise man burns up the bond."
So also elsewhere. Accordingly, since we are given to understand that the Vedic mantras treating of Paramesvara constitute the means to Moksha by way of conducing to the knowledge of the Supreme,through destruction of all sins, the recitation of those mantras should be practised throughout life even by the enlightened sage.
In the above Bhasya Srikantha Acharya is quoting; Shruti says 'If even a Chandala, if he should utter the word 'Shiva', one may talk with him, dwell with him, eat with him.' From which scripture is he quoting this?..