Dr. James Cassidy considered Matthew 28:20a, “teaching them to observe all that I have commanded you,” at the Reformed Forum Annual Theology Conference held on September 28, 2024 at Hope OPC in Grayslake, Illinois. Dr. Cassidy offers a comprehensive exploration of the central role of preaching and teaching in the mission of the church. Rooted in the Great Commission, Dr. Cassidy emphasizes that the work of the church is inseparable from the task of proclaiming and teaching the Word of God. He challenges the common distinction between preaching and teaching, arguing that both serve the same ultimate purpose: the faithful execution of Christ’s command to make disciples. Dr. Cassidy presents a biblical and theological case for viewing preaching and teaching as fundamentally the same activity within the church’s mission. He turns to the New Testament to show how the apostles, including Paul and Timothy, understood their ministry as both preaching the gospel and teaching the whole counsel of God. In this way, the church is called to faithfully declare not only the imperatives of Jesus but also the entire redemptive narrative of Scripture from Genesis to Revelation. This address also covers the broader implications of preaching and teaching, emphasizing that these activities must be biblical, systematic, and polemical. Dr. Cassidy encourages pastors and ministers to preach the whole counsel of God, to structure their sermons with theological coherence, and to boldly defend the Christian faith against false religions and worldviews. In conclusion, Dr. Cassidy underscores that preaching and teaching are the church’s primary tasks in fulfilling the Great Commission, and any other activities must serve or flow from this central mission. This address is a profound reflection on the core identity of the church and its mandate to proclaim Christ to all nations.