“Law is reason without desire.”
Good law is idealized as judgment governed by reason rather than by the changing appetites or personal passions of an individual ruler.
Source details
Politics: A Treatise on Government, Book III, Chapter XVI, William Ellis translation; represented through the 1912 Dent witness / Project Gutenberg #6762. In comparing rule by a person with rule by law, Aristotle says that passion can affect even the best rulers and concludes that law is reason without desire.