Sankt Gallen, Stiftsbibliothek 231, fol. 151 (880-890 A.D.)

St. Isidore of Seville († 636), Etymologiae Book 5.4

Ius naturale <est> commune omnium nationum, eo quod ubique instinctu naturae, non constitutione aliqua habetur, ut viri et feminae conjunctio, liberorum successio et educatio, communis omnium possessio et omnium una libertas, acquisitio eorum, quae caelo, terra marique capiuntur; item depositae rei vel commendatae pecuniae restitutio, violentiae per vim repulsio.  Nam hoc, aut si quid huic simile est, nunquam injustum, sed naturale aequumque habetur. (Natural ius is common to all nations.  It has its origins in nature not in any constitution.  Examples of natural law are the union of men and women, the procreation and raising of children, the common possessions of all persons, the equal liberty of all persons, the acquisition of things that are taken  from the heavens, earth, or sea, the return of property or money that has been deposited or entrusted.  This also includes the right to repel violence with force. These things and similar are never unjust but are natural and equitable.)