Machshirin 6:5-6

Machshirin 6:5

The category of water includes liquids that come from the eye, the ear, the nose and the mouth, urine and waste, whether these things came out with or without one’s knowledge. The category of blood includes blood from slaughtering kosher domesticated or wild animals, or kosher birds, and blood that was let to be drunk (by an animal or a non-Jew). Milk whey is like milk. Rabbi Shimon says that olive sap is like oil because sap always includes oil; Rabbi Meir says it’s like oil even though there’s no oil in it. The blood of vermin is like their flesh in that it can render something impure but it doesn’t render food susceptible to impurity. There’s no other blood like that.

Machshirin 6:6

The following liquids both convey impurity and render food susceptible to impurity: a zav’s discharge, his saliva, his semen and his urine; a reviis of (blood from) a corpse (about 3 oz.); menstrual blood. Rabbi Eliezer says that semen doesn’t render susceptible; Rabbi Elazar ben Azarya says that menstrual blood doesn’t render susceptible; Rabbi Shimon says that blood from a corpse doesn’t render susceptible – if it fell on a gourd, one may simply scrape it off and it remains insusceptible to impurity.