In the late Middle Ages, the letter developed into a literary genre. For humanists like Erasmus, a letter was an appropriate method to start a network and to teach within it. From monastic times religious experiences were exchanged in letters and letters were an expression of spiritual community.

The correspondence of Luther complements many of these forms and possibilities. For the Reformation the letter was the primary medium. Following the lead of the Epistles of Paul, Luther also evolved letters with a particular greeting. The letters of Luther often make use of a pastoral approach.

Approximately 2.600 letters of Luther are known. He wrote a great deal, especially when he was away from Wittenberg. To colleague-theologians and friends he wrote in Latin, to rulers and laymen he wrote in German. In his letters, Luther is modest, involved in various matters and engaged with the people. He is prepared for service and he is clear when some injustice must be named. His letters show that a Christian is nobody’s submissive in faith and he is a free lord; and at the same time he is willing to assist his fellow man, in love.