서신서, or "Epistles," refers to a collection of letters found in the New Testament of the Christian Bible. These letters were written by early Christian leaders, such as 사도 바울 (Apostle Paul), to various communities and individuals to provide guidance, teachings, and encouragement in their faith. The 서신서 includes well-known texts like 로마서 (Romans) and 고린도전서 (1 Corinthians). Each letter addresses specific issues faced by the recipients, offering theological insights and practical advice. Together, they play a crucial role in shaping Christian doctrine and understanding of early church practices.