Because you claimed that the story of creation is in Exodus. While Moses references the story of creation in Exodus to make a point in regards to the Commandment that requires the people to rest on the sabbath, the book of Exodus is not the source of the story.
If I write something that uses a reference to provide evidence for a point that I am trying to make, is it proper to then quote my quote of a reference as a reference as if it were the original source? You said 'the creation story in Exodus'. The creation story is not from Exodus, even though part of it is repeated in Exodus to emphasize a point.
I would like to make a correction. I actually have seen worse misquotes. That part of my statement was an exaggeration, and I apologize for that. Sometimes I need to actually read what I am about to post one last time before posting.