Theology of the Cross (Theologia Crucis) is a central aspect of Martin Luther’s theological research, expressed for the first time during the Heidelberg disputation (1518). In this paper, it is used as a hermeneutical principle to interpret some artistic works by Lorenzo Lotto and Johann Sebastian Bach. There are quite a few reasons to believe that the wood cross painted on the left side of Lotto’s Nativity (1523) was added after Lutheran ideas, coming from central Europe, had penetrated northern Italy.The same link between Christmas and Good Friday is also present in Bach’s Christmas Oratorio (1734-1735): undoubtedly, in this case, one might read it considering Luther’s Theology of the Cross.