in hoc signo vinces

Latin

Calque of Ancient Greek ἐν τούτῳ νίκα (en toútōi níka, “in this, victory”).

(Classical Latin) IPA^(key): /in hoːk ˈsiɡ.noː ˈu̯in.keːs/, [ɪn hoːk ˈs̠ɪŋnoː ˈu̯ɪŋkeːs̠]
(modern Italianate Ecclesiastical) IPA^(key): /in ok ˈsiɲ.ɲo ˈvin.t͡ʃes/, [in ɔk ˈsiɲːo ˈvin̠ʲt͡ʃes]

“in this sign thou wilt win”; “in this sign you will conquer”, said mainly of the cross
- c. 12th century, Geoffrey of Clairvaux, S. Bernardi Vita Prima 5.3.26:
  Tunc beatus Bernardus admota propius manu crucem sanctam quae collo Regis pendebat, accepit, et benedicens ei trino signaculo sanctae crucis, consolabatur eum dicens: Confide, Rex, in hoc signo vinces, et in periculo timoris magni, quale nunquam hactenus expertus es, sine laesione tui hostes evades.
  Then blessed Bernard, his hand moving nearer, took the holy cross that hung about the king's neck, and blessing him with the triple sign of the holy cross he consoled him, saying, “Trust, O king, that in this sign you shall conquer, and in the most fearful peril, such as you have never experienced until now, you shall escape your enemies without injury.”