The Hebrew verb taher means to be or become ritually and morally clean. It is used both for ceremonial purification under the Levitical law and for the inner moral cleansing that the prophets longed for.
Taher is the word David used in his great confession: 'Wash me, and I will be whiter than snow... Purify me (taher), and I will be clean' (Psalm 51:7). It spans the full spectrum from outer ritual (cleansing a leper, Leviticus 14) to inner transformation. The prophets anticipated a new covenant taher when God would cleanse the heart directly (Ezekiel 36:25). This points directly to the work of Christ, whose blood provides the ultimate purification that all Levitical washings only foreshadowed.