Full Idea
Are these things ever the same …or do they vary from one time to another; can the Equal itself, the Beautiful itself, …the real, ever be affected by any change? - It must remain the same. …They can only be grasped by the reasoning part of the mind.
Gist of Idea
Things like the Equal and the Beautiful, which are real, must be unchanging
Source
Plato (Phaedo [c.374 BCE], 78d)
Book Reference
Plato: 'Complete Works', ed/tr. Cooper,John M. [Hackett 1997], p.69
A Reaction
Note the assertion that they are 'real', as well as unchanging. It is hard to make sense of 'the Equal' as a Form. We can more easily see what is in common among beautiful things. The number three is equal and unequal. But see 74d.