Zacharias Ursinus is widely known as the main author of the Heidelberg Catechism (1563). In this thesis Wagner-Peterson analyses for the first time the late period of Zacharias Ursinus’ theology on the basis of his lecture on Isaiah. The author focusses on the methodology, the hermeneutics and theology implicated in this lecture. The results are compared to 16th century commentaries and theological concepts. A comparative study of Ursinus’ earlier writings illustrates a development of his theological concept. Wagner-Peterson thus offers important new insights into exegesis and theology in the period of confessionalism. The older Ursinus appears as a reformed theological teacher, whose intention was to school his students in a life of continuous study of scriptural doctrine. The study of and the obedience to biblical doctrine was essential for Ursinus as a school for living and dying according to God’s providential will.