שולחן ערוך · אורח חיים

What to do with the cut tsitsit and the old talits. This siman has 4 seifim:

Seif 1: tsitsit threads that have been cut — one may throw them into the rubbish (לאשפה), for it is a mitsva without kedousha of the body (מצוה שאין בגופה קדושה); but as long as they are fixed to the talit, it is forbidden to make use of them — for example to tie anything with them or the like — because of ביזוי מצוה. [Gloss: some say (וי״א) that even after they are cut one shall not treat them with contempt by throwing them in a degrading place, but they do not require geniza (Kol Bo); and there are scrupulous ones who place them in geniza — and one who is stringent and meticulous in the mitsvot, blessing shall come upon him (Maharil); and see further on סי׳ תרס״ד סעיף ח׳ ט׳.]

Seif 2: the worn-out mitsva talits — one withdraws from them (בודל עצמו): it is not permitted to wipe oneself with them nor to designate them for a degrading use; but one throws them away, for they are [mere] utensils (כלים) [without kedousha].

Seif 3: it is permitted to enter with tsitsit into the toilet (בית הכסא). [Gloss: all the more so (וכ״ש) is it permitted to sleep in them; some wrote that it was customary not to sleep in a talit bearing tsitsit, nor to give it to a non-Jewish washerman to launder — all this so that the mitsvot not be contemptible to him; but the practice is lenient to sleep in them (Kol Bo).]

Seif 4: one shall take care, when wearing a talit, not to drag its tsitsit.