Unio cum Christo is a central doctrine not only within specific theological traditions but also for its potential in fostering ecumenical dialogue. This paper seeks to explore unio cum Christo from both biblical and historical perspectives. Given its capacity to represent the Christian experience of faith, the potential of this doctrine for ecumenical dialogue should not be underestimated. We will examine the continuity between the medieval Triplex Via and the soteriology of Calvin and Flavel. Despite some notable differences, similarities emerge, particularly concerning the prior condition of repentance. In addition to its ecumenical significance, the concept of preparatory repentance can also serve as a defense against the charge of antinomianism.