acintyam-avyaktam-ananta rupam
śivam praśāntam amṛtam brahmayonim
tathā ādimadhyāntavihīnam ekam
vibhum chid-ānandam arūpam adbhutam

(Who is) unthinkable, unmanifest, of endless forms
the good, the peaceful, Immortal, the origin of the worlds
without beginning, middle, and end, the only one
all-pervading, Consciousness, and Bliss, the formless and the wonderful

~ Kaivalya Upaniṣad, Verse 6
Translation Swāmi Mādhavānanda, from Minor Upaniṣads

"How can one's source, which can be experienced only after the ego-self has been completely annihilated, be thought of, via the ego, as "I am That"? To remain silent in one's "I" [the Self], with the ego destroyed, is the proper course."

~ Muruganar, Guru Vachaka Kovai (740)

“There is no fortune greater than peace; there is no force greater than peace; there is no excellent tapas greater than peace; there is no immortal life greater than [living in] peace.”

~ Muruganar, Guru Vachaka Kovai (796)

The three words, liquidity, sweetness and coolness, which are not opposed to each other, refer only to the single substance, water; which is unique. Likewise, though the Self is described as sat, cit and ānanda as if it has three different natures, upon keen investigation, these three words wil be known to refer only to the one Self.

~ Muruganar, Guru Vachaka Kovai (979)

The Self is the Heart. The Heart is self-luminous. Light arises from the Heart and reaches the brain, which is the seat of the mind. The world is seen with the mind, that is, by the reflected light of the Self. It is perceived with the aid of the mind. When the mind is illumined it is aware of the world. When it is not itself so illumined, it is not aware of the world. If the mind is turned in towards the source of light, objective knowledge ceases and Self alone shines forth as the Heart.

The moon shines by the reflected light of the sun. When the sun has set, the moon is useful for revealing objects. When the sun has risen, no one needs the moon, although the pale disc of the moon is visible in the sky.

So it is with the mind and the Heart. The mind is useful because of its reflected light. It is used for seeing objects. When it is turned inwards, the source of illumination shines forth by itself, and the mind remains dim and useless like the moon in day-time.

~ Talks with Ramana Maharshi (98)

“The pure mind is itself Brahman; it therefore follows that Brahman is not other than the mind of the sage.”

~ Talks with Ramana Maharshi (204)

“By abiding steadfastly in the Heart, a life that is wholly suffused with true love flourishes without any obstruction as one's own nature. Since the illusory association, the veiling ego, has died, this life of love is indeed the splendour of jñāna, the enjoyment of Śiva-svarūpa that shines with extreme calm.”

~ Muruganar, Guru Vachaka Kovai (1091)

“The heart-knot is full of the darkness of ignorance, and it is illusory. When this knot snaps and opens, consciousness, like the sky, surges undividedly, leading to a clear and enduring peace in which the Self shines forth in the Heart. Only the love for the Self that springs forth in the Heart is the true devotion that is full of auspiciousness.”

~ Muruganar, Guru Vachaka Kovai (1209)

“In a heart that has drowned itself in the awareness of true jñāna, which is wholly love, bliss in its fullness will surge forth. Tormenting desires that arise through delusion do not exist there. That life, existing as the extremely pure svarūpa, is wholly peace.”

~ Muruganar, Guru Vachaka Kovai (1093)