The Freedom of a Christian
Von der Freiheit eines Christenmenschen · Martin Luther, 1520
If someone reads only one thing Luther wrote, it should be this. It is short, it is warm, and it contains the entire argument of the Reformation in about seventy-five minutes, in full, at Project Wittenberg, linked below. What we host directly on this site is one passage, checked against a dated edition, while the complete translation awaits that same check.
Luther sent it to Pope Leo X with a conciliatory letter, which tells you something about how fast the situation was moving in 1520. The two sentences above look like a contradiction and are not: the first describes what faith receives, the second describes what love does with it. Everything Lutherans say afterwards about vocation, good works, and Christian liberty unfolds from that pair.
It is also the friendliest door into Luther. There is no scholastic apparatus, very little polemic, and the images (the marriage of the soul to Christ, the good tree bearing good fruit) carry the argument without requiring you to already know the argument.
Where to start
Read the whole thing in one sitting if you can, at the source linked below. If you cannot, the first ten paragraphs and the final third are the essential parts; the middle section on the priesthood of the baptized is worth a second read.
Read alongside
The library tracks which works answer which. This is the conversation this text belongs to.
Treatise on Good Works
Luther’s reply to the charge that grace makes people lazy. Written the same year.
Preface to Romans
Thirty minutes on what faith actually is. The text being read aloud when Wesley’s heart was strangely warmed.
Luther on Vocation
Wingren’s study of how Luther’s theology of vocation lands in everyday life.