Excellent words on this subject from David Murray over at The Gospel Coalition site. He is far clearer on this than the other contributors to the article:
I’m massively encouraged by the church’s renewed interest in preaching Christ from the Old Testament, and especially by the increased willingness to see how Old Testament people, places, events, etc., point forward to Christ. This “types and trajectories” (or redemptive-historical) hermeneutic has many strengths.
However, I’m a bit concerned that an overuse of this tool can give the impression that Christ is merely the end of redemptive history rather than an active participant throughout.
Puritans such as Jonathan Edwards were masters of balance here. In his History of the Work of Redemption, Edwards shows Christ as not only the end of redemptive history, but actively and savingly involved from the first chapter to the last. He did not view Old Testament people, events, etc., as only stepping-stones to Christ; he saw Christ in the stepping-stones themselves. He did not see the need to relate everything to “the big picture”; he found the “big picture” even in the “small pictures.”
I’d also like to encourage preachers and teachers to be clear and consistent on the question: “How were Old Testament believers saved?” The most common options seem to be:
1. They were saved by obeying the law.
2. They were saved by offering sacrifices.
3. They were saved by a general faith in God.
4. They were saved by faith in the Messiah.
Unless we consistently answer #4, we end up portraying heaven as not only populated by lovers of Christ, but also by legalists, ritualists, and mere theists who never knew Christ until they got there. Turning back again in order to go forwards, may I recommend Calvin’s Institutes Book 2 (chapters 9-11) to help remove some of the blur that often surrounds this question.