‘Do not move settled things’; the proverb ‘quieta non movere’ expressing this.
Origin
Mid 18th century; earliest use found in Horace Walpole (1717–1797), author, politician, and patron of the arts. From classical Latin quiēta, use as noun of neuter plural of quiētusquiet + nōn not + movēremove, after the phrase quiēta movēre to disturb settled things (SallustCatiline 21. 1).