On Romans:

“This letter is truly the most important piece in the New Testament. It is purest Gospel. It is well worth a Christian’s while not only to memorize it word for word but also to occupy himself with it daily, as though it were the daily bread of the soul. It is impossible to read or to meditate on this letter too much or too well. The more one deals with it, the more precious it becomes and the better it tastes.”

—Martin Luther, The Letter of St. Paul to Romans, written 1546

Chart source: Mark Barry, Visual Unit