Shevuot 7B

וכתיב התם: ״טמא יהיה עוד טמאתו בו״; מה להלן טומאת מקדש, אף כאן טומאת מקדש.

and it is written there with regard to the red heifer: “Whoever touches the corpse of a man who died and is not sprinkled, he will have contaminated the Tabernacle of God…he will be impure, his impurity is still upon him” (Numbers 19:13). This verbal analogy teaches that just as there the verse is referring to the defiling of the Temple, so too here, the sliding-scale offering is brought to atone for the defiling of the Temple.

ואלא ״בה״ למה לי?

The Talmud asks: But if so, why do I need the term “through which” (Leviticus 5:3)? The Talmud earlier derived from this term that one who is impure and unwittingly eats teruma is not liable to bring a sliding-scale offering. The Talmud has now derived that the sliding-scale offering atones specifically for the unwitting defiling of the Temple. If so, it is obvious that one is not liable for unwittingly eating teruma, and the phrase is superfluous.

לרבות נבלת עוף טהור.

The Talmud answers: The term “through which” serves to include one who was rendered impure by eating the unslaughtered carcass of a kosher bird. Unlike other impure items, which render impure any person who touches them, the carcass of a kosher bird renders a person impure only if he eats it. Therefore, one might have thought he would not be liable for entering the Temple if he was rendered impure by having eaten the carcass of a kosher bird. The extra term is therefore necessary to teach that one is liable.

הא אמרת: ״בה״ מיעוטא הוא! משום דמיעוטא הוא ⁠– אייתר; כתיב: ״או כי יגע״⁠ – דבר נגיעה אין דלאו בר נגיעה לא, וכתיב ״בה״⁠ – מיעוטא; הוי מיעוט אחר מיעוט, ואין מיעוט אחר מיעוט אלא לרבות.

The Talmud challenges: But didn’t you say above that the term “through which” is a restriction? How can you now use it to include additional cases? The Talmud explains: It is precisely because it is a restriction that it includes additional cases. As it is written at the beginning of that verse: “Or if he will touch an impurity of a man” (Leviticus 5:3), which indicates that one who is impure with a form of impurity that can impart impurity through touching, yes, he is liable for defiling the Temple by entering it in his impure state. But if one is impure with a form of impurity that cannot impart impurity through touching, then one would not be liable. Therefore, the verse opens with a restriction, and when the verse continues, and it is written “through which,” which is also a restriction, this constitutes a restriction after a restriction, and a restriction after a restriction serves only to amplify the halakha, applying it to additional cases.