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