Numbers 19:6

The only other passage where cedar wood, hyssop, and scarlet wool appear together is Leviticus 14. That chapter describes another ceremony (also "outside the camp") that resulted in ceremonial purification.

Some scholars suggest Eleazar added cedar wood and hyssop for their aroma. Hyssop is associated with purification (Exodus 12:22; Psalm 51:7; compare Hebrews 9:19). The scarlet yarn, like the red heifer, probably symbolizes blood. Together, the cedar wood, hyssop, and scarlet wool symbolize cleansing.

They made the water for the purification ceremony with ashes of the red heifer (19:9). It might be the same as the water of purification in 8:7 (see also 31:19–24). This ceremony needed the ashes of a red heifer. The color probably represented blood (compare Hebrews 9:13–14).

This section explains how ordinary Israelites can become ceremonially clean again after touching a corpse and avoid defiling the Tent of Meeting (see 9:4–12; Leviticus 17:15; 21:1–4, 11–12). God's holiness demands that the place of his presence remains pure and separate from pollution (compare 1 Corinthians 6:9–11, 18–20).