Shabbat 48B

מה בין זו למגופת חבית. אמר ליה רבא: זה חיבור, וזה אינו חיבור.

What is the difference between this and the stopper of a wine jug, which the rabbis permitted piercing on Shabbat in order to serve wine to guests? There, too, by piercing the stopper, he fashions a utensil. Rava said to him: The cases are not comparable: In this case, the neck opening of a shirt, it is considered a connection, i.e., it is an organic part of the weave of the fabric; whereas in that case, the stopper of the jug, it is not considered a connection. Even though the stopper is sealed in place in the jug, it is a separate entity. When the stopper is pierced, no new vessel is fashioned.

רמי ליה רבי ירמיה לרבי זירא: תנן: שלל של כובסין, ושלשלת של מפתחות, והבגד שהוא תפור בכלאים חיבור לטומאה ⁠— עד שיתחיל להתיר. אלמא שלא בשעת מלאכה נמי חיבור.

R' Yirmeya raised a contradiction before R' Zeira. We learned in a Mishnah: The basting of launderers, garments that a launderer sewed together with loose, temporary stitches to avoid losing them; and a ring of keys; and a garment that was sewn with a thread of diverse kinds, e.g., a woolen garment that was stitched with linen thread, which must be pulled out; even though they are attached only temporarily, as they will all eventually be separated, it is considered a connection with regard to issues of ritual impurity. If a source of ritual impurity comes into contact with one of the garments, they all become ritually impure, until one actually begins to untie them, thereby indicating that he does not want them attached. Apparently, even when these items are not in use, e.g., after the launderer finished laundering the clothes, it is also considered a connection.