Letter 13
4. Illud quoque pari observantia ad sacerdotalis concordiae vinculum ab omnibus volumus custodiri, ut nullus episcopus alterius episcopis clericum sibi audeat vindicare, sine illius ad quem pertinet cessione, quam tamen evidentia scripta contineant: quoniam hoc et canonum definivit auctoritas et ipsa servandae unitatis ratio docet; ne omnis ordo ecclesiasticus per hanc licentiam efficiatur instabilis. [...]
There follow further exhortations to observe discipline and guard peace. A fuller disciplinary guideline the Illyrian bishops will find in the letter of Leo to the vicar of Rome in Illyricum, Anastasius of Thessalonica. The letter is dated to the eighth day before the Ides of January in the year of the consulship of Aetius (for the 3rd time) and Symmachus (i.e. 6 January AD 446).
(Patrologia Latina 54, 666 = Ballerini 1753: 679-680)