a man's home is his castle

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? : —Cicero In English, see Book 4, Chapter 16 of William Blackstone's Commentaries on the Laws of England: : 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?

来源：wiktionary