How do we know that the gospel is complete and doesn't require additional revelations?

The doctrine of the sufficiency of Scripture is a cornerstone of Reformed theology, grounded in 2 Timothy 3:16-17, which states that all Scripture is inspired by God and is profitable for teaching, reproof, correction, and training in righteousness. This indicates that the Word of God is complete and does not require any further revelations or signs. In the context of Acts 19, this is evidenced by the Apostle Paul's ministry, which did not rely on new visions or revelations but rather on the proclamation of the already revealed truth of the gospel. The miracles performed through Paul were special signs that validated his message, but they were not to be seen as additions to the gospel; rather, they affirmed its truth and power. Thus, the authority lies in the Scriptures themselves, fully equipping believers for every good work.