"Have more than you show, speak less than you know" emphasizes humility, discretion, and wisdom by suggesting you build inner substance (possessions, knowledge) without flaunting it, and keep your wisdom to yourself to avoid boasting, letting your actions prove your worth instead of words.
The quote comes from "King Lear" by William Shakespeare, in Act 1, Scene 4, when the Fool advises King Lear:
"Have more than thou showest,
Speak less than thou knowest,
Lend less than thou owest,
Ride more than thou goest,
Learn more than thou trowest,
Set less than thou throwest;
Leave thy drink and thy whore,
And keep in-a-door,
And thou shalt have more
Than two tens to a score."
In the scene, the Fool speaks these lines to King Lear as part of a longer speech filled with pithy advice and wit. The Fool, a character who often uses irony and paradox to speak truth to power, is subtly chastising Lear for his reckless decisions.
From online with editing
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The wise words from the Bard sound somewhat familiar, right? I think the Fool is really a person with 大智若愚. 
So I turned to Maowi the cat and asked him:
Me: Maowi, What does it mean by "Have more than you show"?
Maowi: You have a big bag of treats, but only give me a few each time.
Me: Very good. How about "Speak less than you know"?
Maowi: ... hmmm ...
Me: Ahh, you do understand the Fool! 
Wish All a fun Friday!
