In a sermon on Hebrews 8:10 published on October 31, 1912, the English Baptist pastor Charles Haddon Spurgeon declared: “The doctrine of the divine covenant lies at the root of all true theology. It has been said that he who well understands the distinction between the covenant of works and the covenant of grace is a master of divinity. I am persuaded that most of the mistakes which men make concerning the doctrines of Scripture are based upon fundamental errors with regard to the covenants of law and of grace.” Spurgeon was exactly right, and just as the church at the beginning of the twentieth century needed to hear his words, the church in the twenty-first century desperately needs to hear them as well. The church in our day has largely forgotten, ignored, or denied many of the tenets of covenant theology. But to understand the unity of God’s Word rightly, we must understand covenant theology accurately.