I am often asked by students why the NT quotations of the OT do not match up with what we have in our English OT. There are a number of reasons why this is so. The following are some suggestions about this problem (with a little help from my OT mentor, Walt Kaiser).
First, our OTs are generally translated from the Masoretic text, the traditional Jewish text, the earliest manuscripts of which are from around A.D. 900. Naturally, none of the NT writers had this text. If they knew Hebrew (as Paul did), they cited an earlier version of the Hebrew text, translating it into Greek themselves. This text was not necessarily identical with the text that we have.
Second, we have tried to get our printed Hebrew Bibles as close to the original as possible by comparing the Masoretic Text with manuscripts found among the Dead Sea Scrolls and the early translations of the Hebrew text into Aramaic and Greek. None of the NT writers had this luxury. They simply accepted whatever Hebrew text they had. It is unlikely that many of them owned any parts of the Scripture personally, so they were happy whenever they managed to get their hands on a copy of some part of the Scriptures.
Third, even when a NT writer knew Hebrew, he did not necessarily use that text. He often used the text that his readers would be familiar with. Paul sometimes quotes the Greek version of the OT, the Septuagint (LXX), even though he knew Hebrew and had probably memorized the OT in that language.
Fourth, not all NT writers knew Hebrew. The writer of Hebrews, for example, never quotes from the Hebrew text, so if he knew Hebrew, he has kept the fact well hidden. Thus when we come to Hebrews 1:6, which quotes Deut. 32:43, we discover that the NT quotation does not agree with our English OTs (translated from the Hebrew), but it does agree with the LXX. In many cases the LXX is so close to the Hebrew that we cannot tell if an author was using it or translating the Hebrew himself into Greek, but in this passage there is enough difference that we can tell that our author must have been using the LXX.
Fifth, we must remember that NT writers rarely if ever had the luxury of looking up passages they wanted to quote. Normally they quoted from memory. They were satisfied that they had the general sense of the OT text but would not know if they were not exact in their quotation.
Sixth, in quoting the OT an author at times combines more than one passage in a general paraphrase. For example, Paul in 1 Cor. 2:9 is probably making a loose paraphrase of both Isa. 64:4 and 65:17. In Jas. 2:23 the author joins Gen. 15:6 with the general sense of either 2 Chr. 20:7 or Isa. 41:8. When one is moving along full speed in dictation and is concerned about some issue in the church, a general paraphrase of the OT often did the job without stopping to remember just how the text went.
Finally, we must remember that there are some cases in which the NT author did not intend to quote the OT, but his mind was so filled with it that it flowed out almost as if it were his own words. In these cases no quotation formula (“it is written”) occurs, but we may think that our author is quoting because it is so close to the OT text.
So what are we saying? We are noticing that NT authors were people just like us, but lacking the scholarly tools which we have. They sometimes quoted their favorite version or the version that fit what they were saying, just as we do. They sometimes paraphrased and quoted from memory, just as we do. They sometimes had limited resources available to them, just as is the case with some modern Bible readers. Finally, many of them did not know Hebrew and so had to be satisfied with whatever translation of the Hebrew they could read, just as is the case with many of us. In this we see that God used quite normal human individuals to write the NT. They did not have supernatural knowledge of the OT text but lived within the limitations of their own culture and abilities.
Yet it is the NT documents they wrote that the church has held to be inspired. The teachings of the NT are not inspired because they can prove from the OT that what they say accords with that Scripture; they are inspired because the Spirit inspired what they themselves wrote. None of them are giving their readers lectures on the proper text of the OT. In fact, they are not even giving teaching on OT theology. What they are doing is teaching NT truth and showing that the OT supports the point that they are making. In general this is true, even though they did not have the relatively accurate and carefully researched texts of the OT that we have today. When they appear to be “wrong” (allowing that they interpreted the OT differently then than we do now), we must remember (1) that it could be that they may indeed have a better reading for the text in question than we have in our Bibles and (2) that the Spirit of God who inspired the OT text has every right to expand on its meaning.
The point is that while we may understand why the NT writers cite the OT as they do, it is the NT point that they are trying to make that is inspired in the NT document. Thus, while we may enjoy understanding what is happening and why our OT quotations differ from what we expect, the real issue is whether we are obeying the NT teaching.