Chandogya Upanishad is part of the Sama Veda. There are eight chapters in it. Here are few quotes from Chandogya Upanishad:
Previous to creation all this was being, one only without a second, Name and form were not.
Just as by one clod of clay all that is made of clay is known, the modification being only a name, arising from speech, while the truth is that all is clay.
Just as by one nugget of gold all that is made of gold is known, the modification being only a name, arising from speech, while the truth is that all is gold.
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.
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.
Saint Sanatkumara Quotes from Chandogya Upanishad
When one has faith, only then does one reflect.
When one is single-minded in ones devotion, only then does one have faith. One who does not have single-mindedness does not have faith. One must desire to understand single-mindedness.
When one performs one’s duties only does one have single mindedness.
The infinite is bliss. There is no bliss in anything finite.
Where one sees nothing else, hears nothing else, understands nothing else – that is the Infinite.
Chandogya Upanishad Teachings – Supreme Being Called By Various Names
Just as the salt dissolves in the water, so too the Divine pervades everywhere. It may not be visible, and yet its presence cannot be denied.
This great banyan tree has sprung from a tiny seed. So too, are all beings grown from the seed of the spirit. In the tiny seed, the banyan tree is not visible. So, too, we may not visualize the infinite cosmos, inside the spirit.
Speech, eyes, ears, limbs, life are in union with spirit.
Chandogya Upanishad on Highest Knowledge
Sage Narada went to Sage Sanatkumara to learn about truth, and Sanatkumara inquired what he had studied already.
Narada answered that he had studied the Vedas, Astronomy,
and various other things, yet he had got no satisfaction. Then there was a
conversation between the two, in the course of which Sanatkumara remarked that
all this knowledge of the Vedas, of Astronomy, and of Philosophy, was but
secondary; sciences were but secondary.
That which make us realize the Brahman was supreme, the
highest knowledge. Knowledge of the sciences covers only part of our lives, but
the knowledge which religion brings to us is eternal, as infinite as the truth
it preaches.
Teachings on Creation from Chandogya Upanishad
The Existent was here in the beginning alone and without a second.
It willed, ‘I may be much, let me multiply.’ It brought forth Fire.
The Fire willed, ‘I may be much, let me multiply.’ It brought forth water. Hence wherever a person is hot or sweats, water springs in that spot from fire.
The Water willed, ‘I may be much, let me multiply.’ It brought forth Food. Hence wherever it rains, food becomes plentiful: from water indeed spring food and eatables in that spot.
If something was not quite known, then know it for a combination of these three.