The Gospel in the Old Covenant

"Then Jesus said to them, 'O foolish ones, how slow are your hearts to believe all that the prophets have spoken! Was it not necessary for the Christ to suffer these things and then to enter His glory?' And beginning with Moses and all the Prophets, He explained to them what was written in all the Scriptures about Himself" (Luke 24: 25-27).
So spoke Jesus to the travellers to Emmaus. The incident was captured by Michelangelo Merisi da Caravaggio (1571-1610), in the painting gracing the cover of this book. What was Jesus' message? The entire Old Testament speaks of Him and to Him. As Paul wrote in Galatians ch. 3, Abraham's seed - not seeds, seed - is Christ, and it is to Christ that the promises to Abraham accrue (v. 16). Therefore, it is the church - the body of that Christ - to which the Abrahamic covenant refers.
Is this a species of so-called "replacement theology"? By no means. The church existed just as well in the Old Testament as in the New; it was not, as is too often asserted, founded at Pentecost, replacing Israel. In the Old Testament, fleshly Israel harbored spiritual Israel; in the New, the church has expanded, gone into all the nations. Paul gives the rationale: "hardness in part to Israel has happened until the fullness of the nations may come in" (Romans 11: 25, Literal Standard Version).
This and more are unfolded in this marvellous introduction to full-orbed covenant theology as envisioned by the great spokesman of the Dutch Reformed church, P. J. Hoedemaker.