We know, of course, that in the Koran Jesus was not crucified, that a double was substituted for him. This is based on an immense respect for God: it would be impossible and unworthy for God to allow his Messiah, his Servant, to be killed. This is the difference between two apophatic approaches. For Islam, all theology is negative; beyond the ninety-nine divine names (symbolic of their infinite number), the hundredth is silence. “He is Huwa,” cry the mystics, and it is indeed a cry of silence. Christian apophaticism, on the other hand, is beyond all negation and all affirmation, maintaining an indispensable antinomy. God is so transcendent that he transcends his own transcendence to come to us in the tragedy of death, and, already now, to raise us up. Today, it is history itself, the suffering of the Palestinian and Iraqi people, the crisis in Algeria, which allows some Moslems to sense the mystery of the Cross. In the Middle East, the theme of the Passion often appears in the great Arab poets.
– Clement, Oliver. Conversations with Ecumenical Patriarch Bartholomew I. 207.
It should be noted that there are Islamic traditions in which God is believed to have incarnated. Those traditions, of course, are considered heretical by mainstream Muslims.