a man's home is his castle
Definition from Wiktionary, the free dictionary
Traditional; the sentiment dates back to Roman times:
- quid enim sanctius, quid omni religione munitius, quam domus unusquisque civium?
- What more sacred, what more strongly guarded by every holy feeling, than a man's own home?
- And the law of England has so particular and tender a regard to the immunity of a man's house, that it stiles it his castle, and will never suffer it to be violated with immunity: agreeing herein with the sentiments of ancient Rome, as expressed in the works of Tully; quid enim sanctius, quid omni religione munitius, quam domus unusquisque civium?
Related terms 
- Gregory Y. Titelman, Random House Dictionary of Popular Proverbs and Sayings, 1996, ISBN 0-679-44554-4, p. 229.