Ask five different pastors this question, and you will get five completely different answers. Paul Levy, for instance, reads a couple commentaries all the way through before starting a sermon series. After that, he uses them only when he’s stuck. Others (and this seems to me to be the majority position) advocate that one should only use commentaries at the very end of the process of writing a sermon or Bible study. Oftentimes, the justification for this position is that one must make allowance for the work of the Holy Spirit, and we should not merely parrot what other people say. Some even advocate that no commentaries should be read until after the sermon is written. My experience is a little different.
I find that after I have gone through the text in the original languages very carefully, I still don’t have very many thoughts of my own. I am not much of an original thinker. I really only form my ideas of what the text says in conversation with others who have delved far more deeply into the text than I have.
As with any theological book, one eats the meat and spits out the bones. The same is true for commentaries. By all means, work through the text carefully on your own (and do it first, not least so that you can understand what the commentaries are saying). However, why limit yourself to your own ideas? Why not allow the historical stream of churchly interpretation to feed into your understanding of the text? I usually find that my final position on a text has a very eclectic set of nuggets gleaned from many different sources. I am often surprised at how it works. A commentary from which I got no help for weeks at a time sometimes justifies its very existence in one week where it nails the text and none of the others did. It can be breathtaking at times. Then there are those commentaries that very often have solid insights on almost every page (though these are rare).
To answer the objection about the Holy Spirit is easy. Firstly, the Holy Spirit comes through prayer. I seriously doubt that reading more commentaries constitutes an obstacle that the Holy Spirit cannot overcome. Furthermore, why couldn’t the Holy Spirit be operating through those commentaries to give you what you need? Can the Holy Spirit use the words of dead white European and American males (and a few of them alive still)? There are some excellent female interpreters of Scripture as well, who have written good commentaries (Joyce Baldwin and Karen Jobes spring immediately to mind)
The saddest thing of all in my mind is when a pastor thinks he is so much smarter than church history that he doesn’t need to read what anyone else thought on a passage of Scripture. Really? So you’re smarter than Calvin, are you? Smarter than Augustine? You have the Holy Spirit and they did not? We are not enslaved to any one interpreter. We are not required to believe everything that any non-inspired theologian wrote. Reading them does not mean that we are limited to them. But iron sharpens iron, as the biblical proverb has it. Why allow ourselves to be dulled by refusing to engage in the great centuries-old conversation about the meaning of the text? Limiting ourselves unnecessarily can result in very dull sermons, where so many nuggets in the text are simply by-passed so that the pastor can get up on his hobby-horse.
Make no mistake: there are dangers no matter what position you take on the reading of commentaries. The dangers of reading lots of commentaries are pride, an overdose of explanation, a presentation of too many alternative interpretations (which can easily bewilder a congregation), merely parroting in the sermon what others say, and confusion in one’s own mind about the meaning of the text. The dangers of reading too few commentaries, however, outweigh the dangers of reading too many, in my opinion. For here are the dangers of reading too few: ingrown, idiosyncratic interpretation; missing too many details of the text; application that has no root in the meaning of the text; stream of consciousness preaching; pride and over-reliance on one’s own interpretive skills (which would fall foul of Proverbs’ dictum to lean not on your own understanding); a despising of church history; a denigration of the Holy Spirit’s work in other ages of the church; chronological snobbery. It seems to me that the dangers of reading too many are more easily avoidable than the dangers of reading too few, since they are more obvious. If a sermon is the result of one mind interacting with many minds about the text, is there not a multitude of counselors? Isn’t that safer? I advocate, therefore, and practice an earlier reading of the commentaries in the process of sermon-writing and Bible study preparation. I advocate reading the commentaries (and as many as time and money allow) right after the careful reading of the text in the original languages.