Occasionally, I am part of discussions about whether or not it is helpful or appropriate to use commentaries as part of personal devotions. Here is Princeton theologian B. B. Warfield's (1851-1921) opinion which was originally delivered in a lecture to new students on September 20, 1903. Special thanks to Pastor David Hanson who passed this on after reading it in The Savior of the World. The chapter is titled: "Spiritual Culture in the Theological Seminary."
"You must assimilate the Bible and make it your own, in that intimate sense which will fix its words fast in your hearts, if you would have those words rise spontaneously to your lips in your times of need, or in the times of the need of others. Read, study, meditate on your Bible: take time to it-- much time; spend effort, strength, yourselves on it; until the Bible is in you. Then the Bible will well up in you and come out from you in every season of need."
"It is idle to seek aids for such reading and meditation. The devout and prayerful spirit is the only key to it. Nevertheless there are helps which may be temporarily used as crutches if the legs halt too much to go. ... [He then goes with a paragraph listing and commenting on various devotionals and commentaries like Matthew Henry] ... In the use of such aids it is wise to be constantly on guard, lest on the one side, we permit the aid to supplant the direct use of the Word of God as the basis of our meditation, and on the other, we grow so accustomed to the crutch that we never learn to walk alone. Let neither Matthew Henry nor Charles Spurgeon supplant either the Word of God or the Spirit of God as the teacher of your soul."