Vulgarity is despicable, and one should make every effort to refrain from mentioning negative matters, even incidentally. Not only do the Sages condemn speech of that kind, they even condem listening to it.

Rabbi Yehoshua ben Levi said: A person should never express a crude matter. Indeed, a verse was distorted by the addition of eight superfluous letters in order that it would not be expressed in a crude matter, as it is stated: “From the pure animal, and from the animal that is not pure” (Genesis 7:8). Rav Pappa said: A different verse added nine letters, as it is stated: “If there will be among you a man, who will not be pure due to a nocturnal incident” (Deuteronomy 23:11). Ravina said: Actually, it is ten letters because of the vav in the word tahor [pure]. Rav Aha bar Yaakov said: Yet another verse adds sixteen letters, as it is stated: “As he said: It is incidental; he is impure, as he is not purified” (I Samuel 20:26).

A person should always converse euphemistically….

There were two students who were sitting before Hillel the Elder, and one of them was Rabban Yohanan ben Zakkai. And some say it was before Rabbi Yehuda HaNasi, and one of them was Rabbi Yohanan. One said: Why must one be careful to harvest grapes in a state of ritual purity, but one need not harvest olives in a state of ritual purity? And one said [the same idea, only he worded it differently]: Why must one harvest grapes in ritual purity, but one may harvest olives in a state of ritual impurity? Their teacher said: I am certain that this [first student, who spoke euphemistically, will] issue halakhic rulings in Israel. It was not even a short while later that he issued halakhic rulings in Israel.

Due to the sin of vulgar speech, troubles abound, and harsh decrees are renewed, and the youth of the enemies of Israel die, and orphans and widows cry for help and are not answered….

Rabbi Hanan bar Rava said: Everyone knows why a bride enters the wedding canopy. Nevertheless, anyone who speaks in a vulgar manner about it, even if the angels on High sealed for him a decree of seventy years of good fortune, they will reverse it to bad fortune because of this sin.

Rabba bar Sheila said that Rav Hisda said: Concerning anyone who speaks in a vulgar manner, Gehenna is deepened for him…Rav Nahman bar Yitzhak said: The same applies even to one who hears vulgar speech and remains silent.

Bar Kappara expounded: What is the meaning of what is written: “And a spade shall be for you with your weapons [azenekha]” (Deuteronomy 23:14)? Do not read it as “your weapons [azenekha].” Rather, read it as: On your ear [oznekha], meaning that if a person hears an inappropriate matter, he should place his finger [which is shaped like a spade] into his ears. And that is what Rabbi Elazar said: Why are the fingers of a person similar to spades? So that if a person hears an inappropriate matter, he will place his fingers in his ears.

A Sage of the school of Rabbi Yishmael taught: Why is the entire ear hard and the earlobe soft? So that if a person hears an inappropriate matter, he will bend his earlobe into his ear to seal it.

Rabbi Eliezer ben Yaakov says: If a person is fine and laudable and yet he utters a foul expression from his mouth, to what can this be compared? It can be compared to a large hall that has the opening of a tanner’s sewer fixed inside it. Every passerby says: How fine would this hall be were it not for the tanner’s sewer fixed inside it. The same applies to a fine and laudable person who utters a foul expression from his mouth. (Pesaĥim 3a–b; Shabbat 31a, 33a; Ketubot 5a; Derekh Eretz Rabba, Ben Azzai 1)