Chandogya Upanishad Teachings

That alone which is infinite is Bliss and there is no bliss in the finite. (7.23.1).

Through purity of food comes purity of mind, through purity of mind comes a steady memory of Truth, and when one gets this memory one becomes free from all knots of the heart.’ (7.26.2)

Where one sees another, one hears another, so long as there are two, there must be fear, and fear is the mother of all misery. Where none sees another, where it is all one, there is none to be miserable, none to be unhappy.’ (7.33)

Chandogya Upanishad