Números 19:17 Referencias de la Mishná: Mishnah Kelim, Mishnah Temurah, Mishnah Eduyot & Mishnah Parah

The fathers of impurity are a: sheretz, semen, [an Israelite] who has contracted corpse impurity, a metzora during the days of his counting, and the waters of purification whose quantity is less than the minimum needed for sprinkling. Behold, these convey impurity to people and vessels by contact and to earthenware by presence within their airspace, But they do not convey impurity by being carried.

Hatat water does not become hatat water except with the putting of ashes [in the water]. A doubtful graveyard cannot make another doubtful graveyard. Nor can terumah be made after terumah. A substitute cannot make another substitute. The offspring of a dedicated animal cannot make a substitute. Rabbi Judah says: the offspring of a dedicated animal can make a substitute. They said to him: a dedicated animal can make a substitute, but neither the offspring of a dedicated animal nor a substitute can make a substitute.

Food which is in separate pieces does not combine together [to receive impurity], according to Rabbi Dosa ben Harkinas. But the Sages say: “It does combines together.” One may exchange [ produce of] second tithe for uncoined metal, according to Rabbi Dosa. But the Sages say: “One may not so exchange it.” The hands [alone] need to be immersed for the waters of purification according to Rabbi Dosa. But the Sages say: “If his hands have become unclean his whole body becomes unclean.”