In order to offer a shortened, abridged version of the original passage. This allows audiences to get a general impression of the passage without reading the entire thing.
Answer:
Tools that are sharp (eg knives) get dull as you use them, but when you speak sharply (in a bitter or critical way) often, you overall tend to speak that way more. So, instead of getting less sharp, your tongue is getting sharper.
It will evaporate, condense, then make precipitation
