Purification from uncleanness and defilement
Archimandrite Nikifor’s Biblical Encyclopedia

. Under the Mosaic Law the unclean included lepers, those with discharges, women after childbirth, newborn children, and everything dead; uncleanness passed by contact from them to other persons and objects (Lev. 12:2–6; 15:2; Num. 5:2–3). As a chosen and holy people, the Israelites were to remain apart from all such uncleanness. Various regulations and purification sacrifices were established in the Law for cleansing from them. See Baths, Bathing, and the separate entries Water of purification, Water of jealousy, and others.