This proverb means that what is said cannot be unsaid.

这条谚语告诉我们：话已经说出了口，就无法再收回。

youdao

What is said cannot be easily unsay.

说出来的话不易取消。

youdao

The jester said, "If these wise men do not know how to hide the moon, then the moon cannot be hidden."

VOA: special.2009.03.28

So, they thought about this, and they said, you know, this cannot make sense from the standpoint of the plum pudding model.

他们考虑到这一点，他们说，这是不可能的,如果从布丁模型来考虑的话。

麻省理工公开课 - 固态化学导论课程节选

There were words in there--they said something--of course, we cannot guarantee that they won't go up in value but historically they have always done it or something like that.

他们在文中吹嘘...当然,我们不能保证金币不会升值,但金币的历史行情趋势始终向上

耶鲁公开课 - 金融市场课程节选

Perhaps his words were misconstrued by the general public, but to many Cuban Americans what has been said cannot be forgiven.

FORBES: A Cuban Restaurateur's Comprehension of Ozzie Gullien's Mouth

For his part, Clemens said he cannot in good conscience admit to something he did not do.

NPR: Clemens Denies Drug Use, Pettitte's Account

The producers alliance has said it cannot afford to meet all the writers' demands.

BBC: News Online