And that is exactly what God tried to tell Adam. Paul found that SIN was in his flesh, and all his rants about what was good and evil did not help him at all. Devil will use religion Good and evil sounds so religious. God had a tree of life, so the devil used a tree also. But it is a matter of life, and not good or evil knowledge.
Flesh has no good thing dwelling in it.
Now, Jesus' flesh was seen in the veil of the temple. When Jesus' flesh died, the veil was torn open. The veil, that had cherubims sewn into it, was torn open when Jesus died. Adam could not go in because of his sin and the cherubims protecting the way. Sin was in his flesh.