Shabbat 84B

ודין הוא: ומה פכין קטנים שטהורין בזב ⁠— טמאים במת, מפץ שטמא בזב, אינו דין שיהא טמא במת?! ואמאי, הא לית ליה טהרה במקוה! אמר ליה רבי חנינא: שאני התם הואיל ואיכא במינו.

And it is derived through an a fortiori inference: We know that small vessels do not become ritually impure through the impurity of a zav because they are not designated for sitting, and are too small for the zav to insert his finger into their airspace. If small earthenware pitchers remain pure and are not susceptible to the impurity of a zav, but they do become ritually impure from contact with a corpse; is it not logical that a reed mat, which contracts impurity from a zav, will become ritually impure from contact with a corpse? And why should the reed mat become impure? Isn’t it true that it does not have the possibility of purification in a mikveh? R' Ḥanina said to him: There, in the case of the mat, it is different because there is purification in other vessels of its kind, i.e., other wooden vessels that are made from materials that grow from the earth can be purified in a mikveh.

אמר ליה: רחמנא ליצלן מהאי דעתא: אדרבה, רחמנא ליצלן מדעתא דידך. וטעמא מאי ⁠— תרי קראי כתיבי. כתיב: ״ואיש אשר יגע במשכבו״, וכתיב: ״וכל המשכב אשר ישכב עליו הזב יטמא״. הא כיצד? יש במינו, אף על גב דלית ליה טהרה במקוה. אין במינו, מקיש משכבו לו.

R' Ila said to R' Ḥanina: May the all-Merciful save us from this opinion. R' Ḥanina responded: On the contrary, may the all-Merciful save us from your opinion. And what is the reason that this is relevant? What is the significance of the fact that other vessels of its kind can be purified in a mikveh if the vessel itself cannot be purified in a mikveh? It is because two verses are written. In one verse it is written: “And whoever touches his bed should wash his clothes, and bathe himself in water, and be impure until the evening” (Leviticus 15:5). The verse juxtaposes his bed to himself. Just as he has the possibility of purification through immersion in a mikveh, so too, his bed has the possibility of purification in a mikveh. This teaches that his bed has the same legal status as he does; in order for a bed on which a zav lies to be subject to the impurity imparted by lying, it must be immersible in a mikveh. And in another verse it is written: “Every bed on which the zav lies should be impure; and every vessel on which he sits should be impure” (Leviticus 15:4). This verse includes all beds on which a zav might lie, even one that cannot be purified in a mikveh. How can these two verses be reconciled? If there is purification in other vessels of its kind, even though it itself does not have purification in a mikveh, it is subject to the impurity imparted by lying. However, if there is no purification in other vessels of its kind, the verse juxtaposes his bed to himself. Any vessel that is not like him in the sense that it cannot be purified in a mikveh, is not subject to impurity imparted by lying.