The Old Testament and the Old Covenant are not the same thing. The Old Testament contains the old covenant, but the Old Testament is not only the old covenant. The Old Testament contains the creation story, the protoevangelium, or the declaration of grace in the Garden of Eden, the story of Noah and the covenant with him, promising a common grace to all humans, the election of Abraham, the covenant of grace with him, the history of Israel and the Jews, the prophecies about Israel and the Jews, and the new covenant that would be instituted by the death of Jesus and the promise of the Holy Spirit. The Old Testament contains more than one covenant. One of them is the Mosaic Covenant, which we often call the Old Covenant.
So, when we discuss whether the Old Covenant has passed away, we are not meaning in any way that the Old Testament is cancelled. The Old Testament as well as the New Testament are the scriptures of God. All scriptures are God’s infallible and inerrant word. So, they are the final authority on all matters that concern God’s redemptive plan and purpose. All the Old Testament scriptures are progressive divine revelations, and they are pedagogical for believers in Jesus Christ.