All of Scripture is nothing else than a continuous witness of Christ. “In the volume of the book it is written of Me” (Ps. 40:[7]), something that is repeated in Heb. 10:7. Luke 24:44: “Everything written about Me in the Law of Moses and the prophets and the psalms must be fulfilled.” “Search the Scriptures; it is they that bear witness of Me” (John 5:39). “The testimony of Jesus is the spirit of prophecy” (Rev. 19:10). That is, all prophecies refer to Jesus as the most suitable and ultimate goal. For this reason, Jerome calls Christ “the head of all Scriptures” (Letter ad Algas., q. 11). Augustine (Contra Faust., bk. 16, ch. 22) says: “Every intent of Scripture has to do only with understanding the grace of Christ.” Augustine again, on Psalm 71: “Everything that has been written refers to Christ.” Tractate 9 on John: “He does not understand the Old Testament unless Christ is understood therein.” On the basis of this foundation, a recent theologian teaches: “The Bible is to be read in such a way as if it was written entirely with the blood of Christ.”
Johann Gerhard, Theological Commonplaces: Exegesis IV – On Christ (3)