Sanhedrin 48A

משמשין ממשמשין גמרינן, לאפוקי עגלה ערופה דהיא גופה קדושה.

We derive the halakha governing the accessories relating to a dead person, e.g., a shroud, from the halakha governing the accessories used in idol worship, e.g., the animal sacrificed to the idol. This is to the exclusion of a heifer whose neck is broken, which is itself consecrated for the ceremony taking place in the valley and is not an accessory used in that ceremony.

ואביי, מאי טעמא לא גמר מעבודה זרה? אמר לך: מידי דאורחיה ממידי דאורחיה גמרינן, לאפוקי עבודה זרה דלאו אורחא.

The Talmud asks: And Abaye, what is the reason that he did not derive the halakha by way of a verbal analogy from the halakha governing accessories used in idol worship? The Talmud answers: Abaye could have said to you that we learn the halakha governing something that involves a proper way of conduct, i.e., burying the dead, from the halakha governing something that involves a proper way of conduct, i.e., the rite relating to the heifer whose neck is broken, as these are both mitzvot by Torah law. This is to the exclusion of objects of idol worship, which do not involve a proper way of conduct.

סימן: כפה, נפשיה, דחציבא, בקבריה דיתיר מאבה, בכיסא דאומנא.

§ The Talmud presents a mnemonic for the forthcoming series of attempted proofs concerning the dispute between Rava and Abaye: Scarf; monument; that was hewed; pouch; craftsman.

מיתיבי: כפה שהוא טמא מדרס ונתנתו לספר ⁠– טהור מן המדרס, אבל טמא מגע מדרס. אימא: נתנתו וכרכתו.

The Talmud raises an objection against Rava from a baraita discussing ritual impurity that is contracted by treading: If a scarf is ritually impure with impurity imparted by treading, e.g., after a zav sat or lay down upon it, and its owner then designated it as a cover for a Torah scroll, it is pure of the more severe level of ritual impurity, that which is imparted by treading, even without immersion, because it is no longer an object intended to be lied on or sat upon. But it is still impure with the less severe ritual impurity, that which is contracted by touching that which is treaded upon. This indicates that mere designation has halakhic significance and validity. The Talmud rejects this argument: Say that the baraita should read as follows: The owner of the scarf designated it as a cover for a Torah scroll and wrapped it around the scroll, so that there was not only designation, but an action as well.