Here is a commentary by Venerable Sheng Yen on the Faith In Mind Poem by Seng1 Can2 (3rd Patriarch of Chan Tradition). I find that the commentary is practical, clear, not-over-verbose/theoretical and helpful for practitioners of all kinds.
You may like to read it in sections instead of going through it all at one go because the master seemed to have intended it for those in retreats only so at that point the mind is more calm and receptive. Our minds are more busy so slower reading will aid digestion.
Enjoy,
http://www.terebess.hu/english/hsin3.html