The Hebrew noun ezov (אֵזוֹב) refers to hyssop, a small aromatic plant used extensively in Israelite purification rituals. Scholars identify it most likely with Origanum syriacum (Syrian oregano), a plant with bushy stems suitable for sprinkling liquids in ritual contexts.
Hyssop is one of the most theologically loaded plants in Scripture. It appears at the Passover (Exodus 12:22) — where its branches were used to apply the blood of the lamb to the doorposts. It appears in purification rites for leprosy and corpse contamination (Leviticus 14; Numbers 19). Most memorably, David cries: "Cleanse me with hyssop, and I will be clean" (Psalm 51:7) — invoking the full ritual language of purification as a metaphor for divine forgiveness. At the crucifixion, sour wine was offered to Jesus on a stalk of hyssop (John 19:29) — a detail connecting the cross to Passover and purification: the Lamb's blood, applied with hyssop, cleanses from all sin.