“Tao Te King” by Lao Tsu
Some extracts:

He who knows others is wise.
He who knows himself is illuminated.
He who defeats others is strong.
He who defeats himself is powerful.
He who knows happiness is rich.
He who keeps his path is willful.

Be humble and you will become whole.
Bend and you will become straight.
Empty yourself and you will become full.
Wear yourself out and you will become new.

The wise man does not show off, and so he shines.
He does not make himself known, and so he is noticed.
He does not praise himself, and so he has merit.
And because he does not compete,
none in the world can compete with him.

copied from here