The Warrior's Creed was part of Romulan culture and uttered by soldiers of the Romulan Star Empire.

When Spock infiltrated Romulus he asked the Underground to help him hack into Praetor of the Romulan Star Empire Dralath's personal database. When this was being accomplished, Ruanek uttered the Warrior's Creed but stopped himself when he felt conflicted for betraying the Empire. (TOS novel: Vulcan's Heart)