Agreements must be kept.
Mid 19th century. From post-classical Latin pacta sunt servanda from classical Latin pacta, plural of pactum + sunt servanda ‘(they) must be kept’ (from sunt, 3rd plural present indicative of esse to be + servanda, neuter plural of gerundive of servāre to keep), after pacta et promissa semperne servanda sint whether agreements and promises should always be kept (Cicero De Officiis 3. 92); compare ideo servandum erit pactum conventum thus it will be necessary to keep the agreement made (Justinian Digest 2. 14. 13. 1).