מדרש על סנהדרין 43:11

"shall you place over yourself a king": But is it not already written "Place shall you place over yourself a king"? Why, then, "shall you place over yourself a king"? That his awe be over you — whence it was ruled: One is not permitted to ride on his horse or to sit on his throne or to make use of his sceptre or to see him naked or when he is having his hair cut or when he is in the bathhouse.