Keilim 19:2-3

Keilim 19:2

If the rope extending from a bed is shorter than five handbreadths (about 15”), it is insusceptible to ritual impurity; from five to ten handbreadths (~15”-30”), it is susceptible. From ten handbreadths and up (30”+), it is insusceptible because this is the length of rope with which animals for the first Passover offerings were tied (to the Jews’ beds) and it’s the length with which beds were lowered into a mikvah for immersion.

Keilim 19:3

Rabbi Meir says that if the band that surrounds a bed extends in any amount, it’s insusceptible to ritual impurity; Rabbi Yosi limits this to up to ten handbreadths. The remains of such a band retain its impurity if it’s at least seven handbreadths (~21”) because this is the length from which a belt to attach a donkey’s cover can be made.