Truth will out
The truth will become known eventually.
From Shakespeare's The Merchant of Venice, 1596:
LAUNCELOT: Nay, indeed, if you had your eyes, you might fail of
the knowing me: it is a wise father that knows his
own child. Well, old man, I will tell you news of
your son: give me your blessing: truth will come
to light; murder cannot be hid long; a man's son
may, but at the length truth will out.
See other phrases and sayings from Shakespeare.