His teaching centers on the need for inner conversion. Thus, each person must make a “change of heart”, and God himself will infuse a new spirit. These themes form the basis for the theology of grace and repentance in the Church. Ezekiel also serves as the source of subsequent apocalyptic tradition. The several visions which characterize his prophecy made a very perceptible influence on the Book of Revelation. It is on Ezekiel’s apocalyptic vision that the iconographic portrayals of the Pantocrator have traditionally been based.