“Those who know do not speak. Those who speak do not know.”
— Lao Tzu, Tao Te Ching, ch. 56
What this quote means
A Taoist caution against the ego of expertise. Genuine understanding of the Tao resists being captured in assertion; the more one performs knowledge, the further one drifts from the wordless way of things.
The idea behind it
Wu Wei — The Taoist principle of "effortless action" — accomplishing things by aligning with the natural flow rather than forcing them.
Tao Te Ching is public domain; phrasing varies by translation. Confidence: medium-high.