A commentary, as everyone knows, is a book written by a commentator, and a commentator is one who comments on what God has said, hoping thereby to make us understand what God meant.
The commentary may be good if we know how to use it, harmful if we do not. Its usefulness lies in this, that it provides background material which the average Christian is not able to gather for himself and thus often proves a real aid in the study of the Bible.
But it is not an unmixed blessing. It has at least three serious weaknesses. One is that it soon becomes known as an “authority.” Let a man be quoted often enough and be dead long enough and he is likely to be canonized by his grateful readers and his writings given oracular standing before the Christian public. The pronouncement of a revered commentator often exercises over the mind of a Protestant a sway as tyrannical as that of a papal bull over the conscience of a Catholic.
Another disadvantage of a commentary is that it tends to destroy the art of meditation. We find it easier to turn to the commentary than to brood long and lovingly over a difficult passage, waiting for the light to break. This habit of taking the quick and painless way to knowledge is particularly bad for the minister, for it often sends him into the pulpit with borrowed armor. Even if what he learned is true, he got it by consultation instead of by meditation and the quality is sure to be impaired.
A third weakness of the commentary, or at least of the commentary habit, is that it makes for a uniformity of belief not only on major theological tenets, which is desirable, but on minor ones, which is not. Let a hundred preachers lean on Matthew Henry or Adam Clarke. Then let each preacher be heard by 500 parishioners each Sunday for a year. Result: you have thousands of Christians accepting as divine truth the religious opinions of two good and wise men, opinions which may in the first place have been nothing more than educated guesses. And yet, in spite of these drawbacks, a commentary is a good and useful tool for any Christian to own