And so on the first page of your letter you have indicated that very many baptized by the impious Arians are hastening to the Catholic faith and that certain of our brothers wish to baptize these same ones again.  This is not allowed since the Apostle forbids it to be done and the canons oppose it, and after the cessation of the Council of Ariminum general decrees sent to the province by my predecessor Liberius of venerable memory prohibit it.  These together with the Novatians and other heretics we join to the company of the Catholics through the sole invocation of the sevenfold Spirit by the imposition of a bishop’s hands, just as it was determined in the Synod, which, too, the whole East and West observe.  It is proper that you also do no deviate from this course henceforth, if you do not wish to be separated from our company by synodal decision.

– Pope Siricius

Epistle to Bishop Himerius of Terracina, 385 AD