Kelim, Chapter Twenty-Eight, Mishnah Seven
1) The three (fingerbreadths) square of which they have spoken do not include the hem, the words of Rabbi Shimon.
a) But the sages say: exactly three [fingerbreadths] square.
2) If a patch was sewn on to a cloth by one side only, it is not considered as connected.
3) If it was sewn on by two opposite sides, it is considered connected.
4) If it was sewn on the shape of a gamma:
a) Rabbi Akiva says that the cloth is unclean,
b) But the sages say that it is clean.
5) Rabbi Judah stated: When does this apply? To a cloak, but in the case of an undershirt the patch is regarded as connected if it was sewn by its upper side, but if by its lower side it is not connected.
Section one: In 27:2 we learned that for a piece of cloth to be susceptible to impurity it must be at least three fingerbreadths square. According to Rabbi Shimon, this does not include the hem. Some commentators interpret this to mean that it doesn’t include the strings that come out of the edges of the piece of cloth.
The other rabbis disagree and hold that as long as the piece of cloth is at least three fingerbreadths square, the cloth is susceptible to impurity.
Section two: If a patch is sewn on to the cloth and it is attached only at one side, then it is not considered to be attached to the cloth. If the cloth is impure, the patch remains pure and vice versa.
Section three: If it was sewn on two opposite sides, it is sufficiently attached for it to be considered connected and for impurity to be conveyed from one to the other.
Section four: To be sewn on in the shape of a gamma means that it was sewn on two perpendicular sides. Rabbi Akiva considers this connection to be sufficient to convey impurity from the patch to the cloth and vice versa. But the sages say that if the patch is unclean, the cloth remains clean because this is not sufficient for it to be considered connected.
Section five: Rabbi Judah says that the rule in section two applies only if the garment under discussion is a cloak that is worn above one’s other garments. In such a case, a patch sewn on by one side will not stay well on the garment. But when it comes to an undershirt, if the patch is sewn to the shoulder part of the shirt, it will stay in place and therefore it is considered connected. But if it is sewn by one side only onto the lower side of the shirt, it will not stay in place and therefore it is not considered connected.