A word to the wise?

It implies in a backwards way:

If you're wise you'll listen to these words.

As John Lawler says, the full form of the phrase is a word to the wise is sufficient. A word to the wise is usually employed as a discreet warning in which the ‘word’ is very brief—either the utterance which immediately follows or this utterance itself.

A word to the wise—Paul knows.
A word to the wise—

The sense is “I need say no more than a word to alert you—you’re smart enough to understand what I leave unsaid.”

The context is, "I am warning you about a dangerous condition."

"A word to the wise" means, "A wise person will know what I mean, as soon as I say "beware."

A foolish person will need a lot longer warning/explanation than just one word.

Here's a similar expression

I'm not sure the sense is really about the brevity of the counsel. I think the Latin would have been more emphatic if that were the case. I interpret it more like "experience is the lesson book of fools" - i.e., words count as much or more with the wise than personal experiences do.

Proverbs 17:10 A rebuke strikes deeper into a discerning person than a hundred blows into a fool.

In other words, the wise learn quickly and from few words as in "A word to the wise"

A fool on the other hand cannot learn no matter how many words or even blows.

Hunter S Thompson wrote "A word to the wise is infuriating" I like that. One stupid woman told me I must NOT use the word "negro". She also advised me on whom I should not help financially. But she did graduate from secretarial school so there are areas where I would accept advice from her. Spelling is not one. This aphorism can be interpreted in more than one way since "word" has two different meanings. "May I have a word with you?" Could mean a lengthy conversation or it could mean "Quiet!"

I've always taken the phrase to mean the wise person will take your words to heart and modify future behavior accordingly, while the fool will not immediately learn or choose to grow thereby.