Therefore, the verse states: “That creep,” indicating that creeping animals impart impurity anywhere that they creep, including the sea, as these animals can float in the sea. Consequently, the phrase “upon the earth” is understood as indicating that a sea mouse does not impart impurity.

The baraita raises an alternative interpretation: Or perhaps the term “that creep [hashoretz]” should not be interpreted in this manner, as it could rather be interpreted to mean that any creeping animal that breeds [hammashritz] imparts impurity, but a creeping animal that does not breed does not impart impurity. I shall therefore exclude a mouse that is half-flesh half-earth, i.e., that generates spontaneously from the earth, as it does not breed and therefore does not impart impurity.

But ostensibly, the halakha of a mouse that is half-flesh half-earth is subject to logical inference: Since the verse deems a weasel impure and deems a mouse impure, then just as “weasel” is referring to any animal whose name is weasel, so too, “mouse” is referring to any animal whose name is mouse, even a mouse that is half-flesh half-earth.

Or perhaps go this way: One might think that just as a weasel breeds, so too, “mouse” is referring to a mouse that breeds, excluding one that generates from the earth, which does not impart impurity. Therefore, the verse states: “And these are they which are impure to you among the creeping animals that creep upon the earth.” The term “among the creeping animals” is interpreted as including a spontaneously generated mouse. Therefore, the term “that creep” is interpreted as indicating that creeping animals impart impurity on land and in the sea, and the phrase “upon the earth” teaches that a sea mouse is not included in the category of mouse and does not impart impurity.

One of the Sages said to Rava: Say the interpretation of the verse differently. The term “among the creeping animals” serves to include a mouse that is half-flesh half-earth among those that impart impurity. The term “that creep” teaches that any animal that creeps imparts impurity, and even a sea mouse. And if one should reject this interpretation due to the phrase “upon the earth,” which seems to indicate that a sea mouse does not impart impurity, that phrase teaches that a creeping animal imparts impurity only when it is on land, but if it descended to the sea it does not impart impurity.

Rava said to him: Your suggestion is not logical. According to your opinion, a sea mouse, which is in the sea, imparts impurity. And since you consider the sea a location of impurity, it is impossible to suggest that a mouse does not impart impurity when it is located in the sea. Since both land and sea are places of impurity, what difference does it make for me if the mouse is located here on land, and what difference does it make for me if it is located there in the sea?

The Gemara asks: How can the baraita interpret the phrase “upon the earth” as teaching that a sea mouse does not impart impurity? Isn’t this phrase: “Upon the earth,” necessary to exclude a case of uncertainty involving a floating source of impurity? If a person is uncertain whether he touched a source of impurity that is floating in the water, he remains pure even if the incident took place in a private domain, where a case of uncertain impurity is generally deemed impure. As Rav Yitzḥak bar Avdimi said: The phrase “upon the earth” is written to exclude a case of uncertainty involving a floating source of impurity.

The Gemara answers: The phrase “upon the earth” is written two times in the passage. One instance is written to exclude a case of uncertainty involving a source of impurity that is floating, and the other instance teaches that a sea mouse does not impart impurity.

§With regard to the topic of the eight creeping animals mentioned in the Torah, the Sages taught in a baraita: The verse: “The great lizard after its kinds” (Leviticus 11:29) includes in the category of creeping animals the arvad, a type of snake, and also the creeping animals called nefilim and salamander [salamandera].

Apropos the salamander, which was thought to generate from fire, the baraita continues: When Rabbi Akiva would reach this verse in Leviticus, he would say in exclamation: “How great are Your works, O Lord” (Psalms 104:24). You have creatures that grow in the sea and you have creatures that grow on land. If those in the sea would ascend to the land they would immediately die. If those that are on land would descend to the sea they would immediately die.

Similarly, you have creatures that grow in the fire and you have creatures that grow in the air. If those in the fire would ascend to the air they would immediately die. If those in the air would descend to the fire they would immediately die. Therefore, “how great are Your works, O Lord.”

§The Gemara continues to discuss creatures living in a particular environment. The Sages taught in a baraita (Tosefta, Kilayim 5:10): For every animal that exists on land there is an equivalent animal in the sea, except for the weasel, which exists only on land. Rabbi Zeira said: What is the verse from which it is derived? It is written: “Listen all you inhabitants of the world [ḥeled]” (Psalms 49:2). Dry land is called ḥeled because it is the sole habitat for the weasel [ḥulda].

In continuation of the discussion of creatures living in a particular environment, Rav Huna the son of Rav Yehoshua said: The beavers of the region of Neresh are not from the settled area, because they live only in the water and not on dry land. Consequently, one who eats their meat is not liable to receive lashes for violating the prohibition: “And every creeping animal that creeps upon the earth is a detestable thing; it shall not be eaten” (Leviticus 11:41).

§Apropos the region surrounding Neresh, Rav Pappa said: The people of the city of Neresh shall be placed under excommunication, as they are all wicked, including its fat, its hide, and its tail, i.e., all types of people, both old and young. The Gemara continues to discuss Neresh. The verse states: “Oh land, land, land hear the word of the Lord” (Jeremiah 22:29). Rav Pappa said: This verse is appropriate with regard to the inhabitants of Neresh, as Neresh does not want to listen to the word of the Lord.

Furthermore, Rav Giddel said that Rav said: If a resident of Neresh kisses you, count your teeth to make sure he did not steal one. And if a resident of the city of Nehar Pekod accompanies you on a journey, it is because of the beautiful jacket that he sees on you and wants to steal from you. If a resident of Pumbedita accompanies you on a journey, change your lodging place because there is a concern that he will rob you.

§The Gemara returns to discussing different types of creatures. Rav Huna bar Torta said: Once I went to the city of Va’ad and I saw that the locals were in the practice of placing a snake wrapped around a great lizard in order to breed the two. After a period of time, an arvad, a snake that bites and kills people, emerged from between them.

And when I came before Rabbi Shimon the Righteous, he explained why this crossbreeding created an arvad and said to me: The Holy One, Blessed be He, said: These residents of Va’ad caused the emergence of a creature that I did not create in My world by crossbreeding a snake and a great lizard; so too, I will bring upon them a punishment, the hazard of this uniquely dangerous creature that I did not create in My world, i.e., an arvad.

The Gemara objects: But didn’t the Master say: All different animals whose method of procreation and period of gestation are the same are able to reproduce and raise offspring together. But all animals whose method of procreation and period of gestation are not the same cannot reproduce and raise offspring together. And the gestation period for a great lizard and a snake are not equal.

Rav says: It was a miracle within a miracle that they were able to reproduce and a new creature was born. The Gemara asks: Why is this considered a miracle? It was a calamity because an arvad was born. The Gemara answers: What is meant by a miracle within a miracle? It was a miraculous calamity for the wicked people, to punish them for their actions.

MISHNA: The limb of an animal, with flesh, sinews, and bones, and the flesh of an animal, that were partially severed and remain hanging from the animal do not have the halakhic status of a limb severed from a living animal, which imparts impurity like an unslaughtered carcass, or of flesh severed from a living animal, which is ritually pure, respectively. If one had intent to eat the limb or the flesh, the limb or flesh becomes impure if it comes in contact with a source of impurity, and they impart impurity as food to other foods and liquids, although they remain in their place attached to the animal. But in order for them to become impure, they need to be rendered susceptible to impurity through contact with one of the seven liquids that facilitate susceptibility.