Halacha specifies a number of different levels of impurity; each level can result from touch by an object at one higher level. By this degree, all human hands automatically have second-level impurity (sheni letumah) until washed.Maimonides, Mishneh Torah, Hilchot Avot HaTuma’ot 8:2. Compare Mishnah Shabbat 1:4, Commentary of Rabbi Ovadiah da Bertinoro, ibid., s.v. the Seventh Decree. If (after washing) a person's hands touched a first-level impurity (rishon letumah), those hands become impure as far as the wrist, while the rest of his body remains pure.Maimonides, Mishneh Torah Hil. Avot HaTuma’ot 8:1. Cf. Babylonian Talmud, Hullin 106a-b: "Our Rabbis have taught: 'The sanctification of the hands in the Temple precincts is unto the wrist, [but] for non-consecrated foods unto the joints [of the fingers]; for heave-offering, unto the wrist.'" All that is needed, therefore, is for him to wash his hands in water, and he removes thereby all uncleanness.
