Clement of Rome

1 Clement is the oldest surviving piece of Christian writing outside the New Testament. Around AD 96, the Roman church wrote to Corinth telling them to stop deposing their elders — and the letter doesn't read like scripture, it reads like a pastor writing a problem letter. That's invaluable. It shows what the second-generation church actually believed about church order, succession, and authority, before any of those things became contested. Some early Christian communities read it alongside the New Testament for centuries.