First Epistle of Clement to the Corinthians. Written during the apostolic age and read alongside scripture in many local churches prior to Nicea, Clement I explicitly states in its central chapter (44) that the process by which the episcopal college succeeded the apostolic college was established by the apostles themselves.
Hmmm...where do you get "apostolic college" and "episcopal college" out of Clements writing in chapter 44? Just curious, not debating you.