Quote: Docetism and Islam

One attempt to reconcile the Gnostic doctrine [of the
unreality of evilness] of matter with the apostolic teaching
about Christ was the theory that the body which our Lord took
at His coming into the world was not a real body but a phantom
one. He only seemed to inhabit a material body, and from the
Greek word dokein ["to seem"], people who held this theory
were known as Docetists. But if Christ's incarnation was
unreal, His death and resurrection were also unreal; and the
whole gospel message was thus evacuated of its truth and
power: one unhappy legacy of this short-lived phase of
Christian heresy remains to bedevil Christian witness to
Muslims up to the present day. For when the Koran says of
Jesus that "they did not kill Him, nor did they crucify Him,
but they thought they did," we may infer that Muhammad was
indebted for this idea to a Christian source tainted with
Docetism.
... F. F. Bruce (1910-1991), The Apostolic Defence of the
Gospel [1959]