Barth described theology as “an act of penitence and obedience” that works through “an attitude of prayer.” And he kept that Lenten image of theology before him by hanging a copy of the Isenheim Altarpiece over his desk. Matthew Boulton explains this in his God Against Religion: Rethinking Christian Theology Through Worship (Calvin Institute of Christian Worship Liturgical Studies) :

“the Isenheim Altarpiec e is a multilayered structure, with two sets of wider wings that close toward the center, like a cupboard within a cupboard. Grunewald painted his Crucifixion on the outside of the wider set of these doors, so that the work was only visible when the altarpiece is closed, as it would be, for example, during the Lenten season. Once the outer doors were opened up, however, a triumphant triptych is revealed: on the central panel, an angelic orchestra plays in celebration of the Madonna and child, and flanking this scene, the two outer wings - now open - display the Annunciation and the Resurrection. Thus, for Grunwald, the stark disgrace of the crucifixion actually ‘opens up’ on the divine gifts of the Incarnation and Resurrection. Human defeat gives way to victory.”

Barth “kept the Lenten image before him as he pursued his theological work” and thus “kept before him the hidden triptych, the saving work of Jesus Christ veiled within and behind the appalling work of humankind apart from God. Barth could not actually open up the reproduction over his desk, but the vertical seal between the panels, hope’s thin line running through Christ’s body, was always visible.”