Three things cannot be hidden, the sun, the moon, the truth.
A paraphrase from “The Book of the Threes” :
Monks, there are these three things which shine forth for all to see, which are not hidden. Which three?
The disc of the moon shines for all to see; it is not hidden. The disc of the sun does likewise. The Dhamma-Discipline [dhamma-vinaya] of a Tathagata [Buddha] shines for all to see; it is not hidden. These are the three things.
F. L. Woodward and F. M. Hare, Tr. Gradual Sayings (Anguttara Nikaaya). Pali Text Society. Volume 1.