Full Idea
The best things (such as a god, a healthy body, or a good soul) are least liable to alteration or change.
Gist of Idea
The best things (gods, healthy bodies, good souls) are least liable to change
Source
Plato (The Republic [c.371 BCE], 380e)
Book Reference
Plato: 'Complete Works', ed/tr. Cooper,John M. [Hackett 1997], p.1019
A Reaction
Sounds a bit circular. They are unlikely to qualify for the 'best' group of they keep changing. We wouldn't praise good health which only last half an hour.