Keilim 17:12-13

Keilim 17:12

The Sages instituted a larger measure for the following: a scoopful of rotting human remains (to convey impurity) refers to a large medical instrument; the half-bean measure of tzaraas (“leprosy” but not really) refers to the Cilician bean; one who eats the volume of a large date on Yom Kippur refers to the the date with its pit; the holes to purify skins for wine and oil must be as large as their big plug; the size of a hole in a wall that was not made by human hands (to allow impurity to pass through) is the size of a large fist, specifically that of Ben Batiach. Rabbi Yosi said that the size of such a hole is as big as a large human head. The size of a hole made by human hands is the thickness of the large drill in the Temple chamber, which is the size of an Italian pundion, a sela of Nero or the thickness of a hole in a yoke.

Keilim 17:13

Rabbi Akiva says that all utensils made of sea creatures or sea plants are insusceptible to ritual impurity except for those made of seals because seals seek refuge from predators on dry land. If one made utensils from something that grows in the sea and attached them to something that grows on land – even as much as a thread or a string – if that thing is susceptible to ritual impurity, then the entire utensil is susceptible.