Please help me find a quote from ancient Greece. We'll discuss it later.

[abcd]

Hi. I was reading books about ancient Greece or translations of original sources when I came across sentences like these: How deep is the water? [Step in and] it would show you.
That is my paraphrase, but I don’t think I stray from the original text too much. Now let me give you the context: two men are about to cross a river. One man asks the other: “How deep is the water?” The other replied, “[Step in and] it would show you.” This is some ancient saying, meaning personal experience/practice’s very important. Now I don’t remember where they come from. Could anybody give me the source of this saying? Thank you.
Please don’t delete this post because this is not just a help-me post. I’ll discuss this quote with others after I locate it.

[Scott Mayers]

Hi. I was reading books about ancient Greece or translations of original sources when I came across sentences like these: How deep is the water? [Step in and] it would show you.
That is my paraphrase, but I don’t think I stray from the original text too much. Now let me give you the context: two men are about to cross a river. One man asks the other: “How deep is the water?” The other replied, “[Step in and] it would show you.” This is some ancient saying, meaning personal experience/practice’s very important. Now I don’t remember where they come from. Could anybody give me the source of this saying? Thank you.
Please don’t delete this post because this is not just a help-me post. I’ll discuss this quote with others after I locate it.

What is the signicance to the original author? It might help to know more information about the motive of your question. Such a statement seems like it is related to 'pragmatism'. Maybe Google or similar search for, "Greek + pragmatist" as a start.

[Impenitent]

"You cannot step into the same river twice" - Heraclitus

"I drank what?" - Socrates

-Imp