Here is a great article on a correct understanding of interpreting the Bible according to its canonical context. This helps all students of Scripture undrstand what is meant by
Bifurcation of the material in the two Testaments
The Unity of the covenants
I love some of these quotes in this article including:
Why could not the Old Testament revelation be thought of as the grain of sand, which, after entering the oyster of progressive revelation, has the pearl of additional and deeper concepts added to it without necessarily canceling out the original grain of sand (Fuller 1957, 233)?
The history of exegesis seems generally to demonstrate that when the sensus literalis of Scripture has been defined in a positive and more than woodenly literal way (cf. especially Augustine and Luther), resulting in a synthesis of grammatical, historical, and theological understandings, a flourishing of the exegetical discipline and a renewal of dynamic biblical theology has recurred (Scalise 1989, 65).
The two Testaments are bound together by their common witness to the unfolding revelation of God's character, purpose, and plan. But the salvation wrought by God through Christ is the fulfillment of `Old Testament' history, law, and prophecy .For example, Hebrews 3:7-4:8 employs a typological significance of "land." Based on the pattern of Psalm 95, throughout the passage the word "land" is replaced with the word "rest." It is significant that in the patriarchal promises x;Anm' is never used to describe the land. x;Anm' is introduced once positively in Deuteronomy to describe the land as hx'WnM.h (Deut.12:9), and once in a warning passage that disobedience would result in ytix'Wnm.-la,. !Waboy>-~ai (Psalm 95:11).(Moo 1986, 196)
John Davis : Hermeneutical Issues in the Dispensational Understanding of the Abrahamic Covenant - Quodlibet Journal