In almost every New Testament book the author has cited a passage from the Old Testament. The NT author used the Old Testament in order to offer proof that Jesus of Nazareth was, and is, in fact Israel’s Messiah; or that some aspect of Jesus’ life, ministry and kingdom accorded with the predictions and expectations of the Old Testament. An example is Matthew’s citation of Micah 5:2 that Matthew used in order to argue that Jesus’ birth fulfilled prophecy. So we always tell our students that in their studies when they come across an Old Testament citation in a New Testament book, the first thing they should do is go back to the Old Testament and see how that text was used. Then ask the question, “How does this OT text further the NT author’s argument?”
But, invariably, the student(s) return to the staff, open Bible in hand, and say, “I looked up the OT passage, and that’s not even what it says! It seems that the NT author is taking this passage out of context! He is breaking the rules of interpretation that we learned in the seminar. How can he do that?!” They have, at one level, observed correctly. Paul’s citation of Psalm 68:18 is not how Psalm 68:18 reads in the OT. Matthew (2:15) claims that Jesus “fulfills” Hosea 11:1; yet Hosea 11:1 isn’t even a “predictive” prophecy. And Paul argued for the use of tongues by citing a passage from Isaiah (28:11-12) that is about how Yahweh will use the Assyrians to punish the drunkards and scoffers. What’s up with that?!
How New Testament authors used the Old Testament is a fascinating area of Biblical studies. Attempting to get into the mind of the New Testament authors to understand how they read and used the Old Testament is crucial to our understanding their New Testament argument. New Testament authors knew their OT very well; they did not rip OT texts out of context, neither did they ignore the original meaning an/or audience of the OT texts they cited. They were brilliant writers who were immersed in their Story and their scriptures. The question(s) for us, as 21st century Bible interpreters is, “How did this NT writer read their OT? What was their interpretive method?”
To help us get a handle on how to approach the question(s) I would highly recommend Three Views On The New Testament Use Of The Old Testament, by Gundry, Berding and Lunde (Zondervan, 2007). The book is a very good primer into the discussion of how New Testament writers understood and used their OT. I suggest this so that perhaps next time we have an answer for the student who objects, “[Matthew/Paul/Peter] is a terrible interpreter! He is doing exactly what you said we can’t do!”