It was explained to me on this thread that God writes in words that have meaning to us. That is, when He says "Day" he is referring to our 24 hour day. Thus when he says "rest" he means that he has to take a break because He is tired. Why would God be tired?
A 'rest' does not mean 'tired.' A physical body needs rest, a spiritual one doesn't. You have inserted a meaning to the word which is not in the scriptures.