פירוש על שבת 43:5

From one lamp to another lamp: [Lamps] of Channukah, as its reason will be explained later.

Rav said, "One may not untie tzitzit from [one] garment to [another] garment": It is not necessary [to say] that it is forbidden if it is an obligation upon the garment; but even if it is an obligation on the person, it is forbidden as well. It is as we find with a mezuzah, that the one who took it was punished - in Bava Metzia (102a) at the end of the chapter [entitled] HaShoel - even though it is an obligation on the room. And Shmuel said that we may untie it: Even though Shmuel himself holds that it is on a obligation on the cloak, we remove them nevertheless; since he does it for the need of another garment. And concerning the mezuzah - such that he is punished - perhaps he did not have in mind to place it in another house. Or also (another answer), a mezuzah is different, since it is made to protect [one] from damaging spirits. And even though, according to everyone, we do not untie [tzitzit] when it is not to place them on another garment - that which is customary to untie the tzitzit from the cloaks of the dead is not difficult. For we only do not untie them from a cloak of one who is alive, as he is someone obligated.

Untie: To take the tzitzit from an old cloak (talit) to a new cloak. And in Menachot, it explains the reason of the one that forbids [this].

The law is in accordance with Rabbi Shimon: Since he said [that] something that one did not intend is permissible, even though he made a ditch - which is a derivative of plowing or building. And because the law follows Rav regarding prohibitions in the whole [Talmud] except for these three, they are mentioned together.