Knowledge is an inner fortification that enemies cannot destroy, and is the ultimate impregnable defense. (Tirukkural, 421)
The shrine of the body should not be left dark; one should illumine it with the lamp of Wisdom. (Sri Ramakrishna)
The non-dual Consciousness is called the Supreme Truth by enlightened sages; it is also termed Brahman (by Vedantins), Paramatman (by yogis), and Bhagavan (by devotees). (Bhagavata, 1.2.11)
For the person who has realized the Self in which all beings become the Self what delusion and what sorrow can remain for that seer of oneness? (Isha Upanishad, 7)
He by whom It is not known, knows It; he by whom It is known, knows It not. It is not known by those who know It; It is known by those who do not know It. (Kena Upanishad, 2.3)
There is one who is the eternal Reality among non-eternal objects, the one [truly] conscious Entity among conscious objects, who, though non-dual, fulfils the desires of many. To the wise who perceive Him within themselves belongs eternal peace, unto none else. (Katha Upanishad, 2.2.13)