"When something has been said in Latin..."

For years I have heard this old saying, supposedly well-attested, though I don't know the reference:

"When something has been said in Latin, it has been said forever."(or, "When something is said in Latin, it is said once and for all".)

I used to do a little Latin. These days I am more a fan of Greek. But I speak Spanish almost daily, so my Latin, which is from a while ago, gets quite a bit of interference from Spanish.

But, after all, "cuando se ha dicho algo en Español, se lo ha dicho por siempre."

Latin for this anyone?