quis custodiet ipsos custodes

• (Classical) IPA^(key): /kʷis kusˈtoː.di.et ˈip.soːs kusˈtoː.deːs/, [kʷɪs̠ kʊs̠ˈt̪oːd̪iɛt̪ ˈɪps̠oːs̠ kʊs̠ˈt̪oːd̪eːs̠]
• (modern Italianate Ecclesiastical) IPA^(key): /kwis kusˈto.di.et ˈip.sos kusˈto.des/, [kwis kusˈt̪ɔːd̪iet̪ ˈipsos kusˈt̪ɔːd̪es]
• (Classical) IPA^(key): /kʷis kuːsˈtoː.di.et ˈip.soːs kuːsˈtoː.deːs/, [kʷɪs̠ kuːs̠ˈt̪oːd̪iɛt̪ ˈɪps̠oːs̠ kuːs̠ˈt̪oːd̪eːs̠]
• (modern Italianate Ecclesiastical) IPA^(key): /kwis kusˈto.di.et ˈip.sos kusˈto.des/, [kwis kusˈt̪ɔːd̪iet̪ ˈipsos kusˈt̪ɔːd̪es]

quis cū̆stōdiet ipsōs cū̆stōdēs?

1. “Who guards the guards?”, “Who watches the watchers?”
   • late 1st or early 2nd century CE, Juvenal, Satura VI, lines 347–348:

     audio quid ueteres olim moneatis amici, 'pone seram, cohibe.' sed quis custodiet ipsos custodes? cauta est et ab illis incipit uxor.

     I hear always the admonishment of my friends: "Bolt her in, constrain her!" But who will guard the guardians? The wife plans ahead and begins with them.

• Quis custodiet ipsos custodes? on Wikipedia.Wikipedia