“下不为例”，汉语成语，指某件事做了以后，下次不能再这样做。有提醒、警告、只能通融这一次的意思。可以翻译为“not serve as a precedent; not to be taken as a precedent; not to be repeated”等。

例句：

我保证下不为例。

I promise not to do it again.

只此一遭，下不为例。

Only this time and no more.