I thought this was interesting. Here's Newton's comment on the use of commentaries, in a letter to a fellow minister dated November 21, 1757, when Newton was 32:

...let us endeavor to keep close to God, to be much in prayer, to watch carefully over our hearts, and leave the busy warm spirits to make the best of their work. The secret of the Lord is with them that fear Him, and that wait on Him continually; to these, He will show His covenant, not notionally, but experimentally. A few minutes of the Spirit's teaching will furnish us with more real useful knowledge than toiling through whole folios of commentators and expositors. They are useful in their places and are not to be undervalued by those who, perhaps, in general, do better without them. But, it will be our wisdom to deal less with the streams and be more close in applying to the fountain-head. The Scripture, itself, and the Spirit of God, are the best and the only sufficient expositors of Scripture. Whatever men have valuable in their writings, they got it from hence; and the way is as open to us as to any of them. There is required nothing but a teachable, humble spirit; and learning, as it is commonly called, is not necessary in order to this...

Not exactly a pietistic approach, but close...

__________________
Richard T. Zuelch, M.Div
Ruling Elder, OPC (not currently serving)
Westminster Presbyterian Church, CA (OPC)
www.reiterations.wordpress.com
www.foft.wordpress.com

Faith and repentance are born together and aid the health of each other. - Charles Spurgeon (1834-1892), on July 23, 1865