Overview
A quaternion (Greek: tetradion) was a small Roman military squad of four soldiers. These units were commonly used for guard duties, prisoner transport, and security assignments throughout the Roman Empire. In Acts 12, quaternions were specifically tasked with guarding Peter in prison.
Key Scriptures
"So Peter was kept in prison, but prayer for him was being made earnestly by the church to God." (Acts 12:5, NASB)
"And when Herod was about to bring him out, on that very night, Peter was sleeping between two soldiers, bound with two chains, and sentries before the door were guarding the prison." (Acts 12:6, ESV)
"Peter therefore was kept in the prison: but prayer was made without ceasing of the church unto God for him. And when Herod was about to bring him forth, the same night Peter was sleeping between two soldiers, bound with two chains: and the keepers before the door kept the prison." (Acts 12:5-7, KJV)
Application
Understanding Roman military organization helps us appreciate the miraculous nature of Peter's deliverance from such secure, well-guarded captivity.