Our Gemara on Amud Aleph reports that Rabbi Yosei would use the following verse in Mishley (24:26) to praise cogent Torah arguments:
שְׂפָתַ֥יִם יִשָּׁ֑ק מֵ֝שִׁ֗יב דְּבָרִ֥ים נְכֹחִֽים׃
Giving straightforward reply Is like giving a kiss.
How is a lucid torah argument compared to a kiss? Rashi on our Gemara says it is worthy of a kiss. Tosafos explains that it is not the kiss itself, but rather the gesture of pursing one’s lips together. That is, the instinctive body language displayed when a person finds himself unable to respond. In other words, the logic of the argument was so powerful that the disputant while still wanting to say something, found himself tongue-tied and unable to refute the argument.
The Sefas Emes (Devarim 22:9) uses the idea of pursed lips, but turns it around. Sometimes, he says the best with rebuke is by pursing one’s lips and remaining silent. He says that the Aravos leaves we use on Succos look like lips. We take two aravos to remind us of the two forms of expression. Sometimes we use our mouths in a forthright way and communicate directly. There are times when being assertive is appropriate and effective. And then there are times where we use our lips by keeping them closed, and our rebuke might be more subtle. This is also reminiscent in the duality of Aharon and Moshe. Moshe gave open rebuke, while Aharon’s rebuke is more subtle, and he has known for a remaining silent despite incredible provocation (see for example, VaYikra 10:3 “And Aharon remained silent.”)
This reminds me of an incident that I witnessed firsthand, regarding my father Z”L’s ability to remain quiet and listen actively. Dad was a great believer in listening, and was careful to not allow his urge to speak and offer advice overshadow and stifle the other person’s process. He usually led by quiet example, not by criticism. As one example, he made sure to never speak during davening, from the first beracha to the last kaddish. One time, a man who clearly had a lot on his mind, spent the entire davening chattering away at him. Every now and then, as the man would pause for breath or perhaps to mumble a few Hebrew words, he would say, “Rabbi, what do you think?” Father would not shush the person, he just would smile, and show an inflection that looked like he understood or was reflecting upon it. At the end of davening, the man said, “Rabbi Feuerman, you know what I like about you? You say the smartest things!” I can attest my father has not said one word.