As described in this article, the rabbis of antiquity applied the term “holy” to two different but overlapping concepts: one concerned with a hierarchical arrangement of people, places, days, and objects, the other linked to morality, observance of Jewish law, and acts of loving kindness.
The root k-d-sh, the source for the Hebrew word kedushah, or holiness, occurs an intimidating 9,324 times in the Babylonian Talmud. Yet despite (or perhaps because of) the frequency with which this root appears, it is an especially difficult task to pin down its meaning. K-d-sh rears its head in discussions of sacrifices (where it represents highly regarded offerings reserved generally for those in a state of priestly purity), marriage (as part of the still-used formula by which a marriage is put into effect), prayers, and martyrdom, among other things. It is used to refer to God, the Temple in Jerusalem, and the Hebrew language. For the modern Jew trying to grasp what holiness might have meant for the great rabbinic sages, the diversity of uses for this verbal root can prove to be a frustrating obstacle.
The twentieth-century rabbinic scholar Max Kadushin offered an attempt to make sense of holiness in the rabbinic context in his work Worship and Ethics. According to his schema, holiness for the rabbis came in essentially two sorts, hierarchical holiness and nonhierarchical holiness. Hierarchical holiness was that holiness associated with people, places, days, and objects. The defining characteristic of this hierarchical holiness is, as it name implies, the possibility of declaring, within each of these categories, one item to be of greater holiness than another. Consider, for example, the mishnah in Tractate Megillah of the Babylonian Talmud (25b-26a):
Residents of a city who sold the city square may buy with its money (i.e. the profit from the sale of the square) a synagogue; [if they sold] a synagogue, [they may buy] an ark…[if they sold] scrolls [of the prophets], [they may buy] a Torah scroll. But if they sold a Torah scroll, they may not buy scrolls [of the prophets]…[if they sold] an ark, [they may not buy] a synagogue, [if they sold] a synagogue, [they may not buy] a city square…