Here's a couple of lines from one of the most important pieces I ever read on biblical interpretation to that effect. It was originally delivered in 1989 by Joseph Ratzinger, the future "Benedict XVI".
"A constitutive element of the [New Testament] is the awareness of being in unity with the entire witness of the Old Testament, which only now can be understood as a unity and as a meaningful whole. And indeed, any interpretation of the New Testament has to let itself be measured by the question of whether it can be consistent with this fundamental conviction. When this cannot be done, any possibility of understanding the inner logic of the New Testament writings has been excluded from the outset."
--Joseph Cardinal Ratzinger, "Biblical Interpretation in Conflict: The Question of the Basic Principles and Path of Exegesis Today", reprinted in God’s Word: Scripture—Tradition—Office (ed. P. Hünermann and T. Söding; trans. H. Taylor; San Francisco: Ignatius Press, 2008), 105.