The Tao Te Ching (Dao De Jing) is an 81-chapter text by Laozi, dating to the 6th century BCE. At about 5,000 Chinese characters, it's the foundational text of philosophical Taoism.
Core concept: the Dao (Way) — the origin and operating principle of the universe. "The Dao that can be told is not the eternal Dao." It advocates wu wei (non-forcing), highest goodness like water, and enough-is-enough.
Ch.1: The Dao that can be spoken. Ch.8: Highest goodness is like water. Ch.33: He who knows others is wise; he who knows himself is enlightened. Ch.44: Enough does not disgrace; stop does not endanger. Ch.76: The soft overcomes the hard.
Don't read it all at once. One or two chapters daily, reflected in life. The Tao Te Ching is not information — it's wisdom that must be tested in living.