But this is not mere 'effect' we're talking about. This is the deity's mode of operation as well - which spans time - 7 days of "creation", etc. - the span of time at a time when there is no one to be concerned about "effects". This is a distinction that should not be downplayed.
Resting itself is a time-based activity. You don't rest unless time has an influence on you.
Again, effects of the eternal in the temporal are experienced in time. And the changes in the temporal world do not necessarily mean the eternal has changed. For a somewhat analog, consider the laws of physics. They don’t “rest” when a reaction stops.