Full Idea
If nothing that comes to be can sidestep the now, whenever a thing 'is' at this point, it always stops its coming-to-be and then is whatever it may have come to be.
Gist of Idea
What is becoming can't avoid the now, and then its ceases to become, and is itself
Source
Plato (Parmenides [c.366 BCE], 152c)
A Reaction
Just common sense, but interesting that Plato works so hard to precisely identify the stages of becoming and being.
Book Reference
Plato: 'Parmenides', ed/tr. Gill,M.L./Ryan,P. [Hackett 1996], p.159