The picture shows the central panel of the first view of the Isenheim Altarpiece.
Art for Grünewald did not consist in the search for the hidden laws of beauty - for him it could have only one aim, the aim of all religious art in the Middle Ages - that of providing a sermon in pictures, of proclaiming the sacred truths as taught by the Church. The central panel of the Isenheim altarpiece shows that he sacrificed all other considerations to this one overriding aim. Of beauty, as the Italian artists saw it, there is none in the stark and cruel picture of the crucified Saviour. Like a preacher at Passiontide, Grünewald left nothing undone to bring home to us the horrors of this scene of suffering: Christ's dying body is distorted by the torture of the cross; the thorns of the scourges stick in the festering wounds which cover the whole figure. The dark red blood forms a glaring contrast to the sickly green of the flesh. By His features and the impressive gesture of His hands, the Man of Sorrows speaks to us of the meaning of His Calvary.
His suffering is reflected in the traditional group of Mary, in the garb of a widow, fainting in the arms of St John the Evangelist, to whose care the Lord has commended her, and in the smaller figure of St Mary Magdalene with her vessel of ointments, wringing her hands in sorrow. On the other side of the Cross, there stands the powerful figure of St John the Baptist with the ancient symbol of the lamb carrying the cross and pouring out its blood into the chalice of the Holy Communion. With a stern and commanding gesture he points towards the Saviour, and over him are written the words that he speaks (according to the gospel of St John iii. 30): 'He must increase, but I must decrease.'
There is little doubt that the artist wanted the beholder of the altar to meditate on these words, which he emphasized so strongly by the pointing hand of St John the Baptist. Perhaps he even wanted us to see how Christ must grow and we diminish. For in this picture, in which reality seems to be depicted in all its unmitigated horror, there is one unreal and fantastic trait: the figures differ greatly in size. We need only compare the hands of St Mary Magdalene under the Cross with those of Christ to become fully aware of the astonishing difference in their dimensions. It is clear that in these matters Grünewald rejected the rules of modern art as it had developed since the Renaissance, and that he deliberately returned to the principles of medieval and primitive painters, who varied the size of their figures according to their importance in the picture. Just as he had sacrificed the pleasing kind of beauty for the sake of the spiritual lesson of the altar, he also disregarded the new demand for correct proportions, since this helped him to express the mystic truth of the words of St John.